Positive side of climate change facts, after two years of action, heading for 3°C with 1.5°C well within reach
Robert Walker
Almost nobody seems to report the positive side of our recent climate change action. As someone who followed the topic before Kyoto, what happened since 2016 was remarkable. The change in attitude, pace of action, at last gives much hope that we can rise to the challenge. I have never in my life seen such a coming together of nations worldwide to solve a problem.
Before 2015, it seemed close to hopeless that we would rise te challenge. Many individual actions, but nothing compared to the scale of the problem. Now we are doing so much, and acting together globally in many ways. Yet the more we act, the more the publicity seems to focus on what we aren't doing, and almost never on our successes.
That's the key to the Paris agreement, to constantly build on successes. The pace is accelerating. Month on month it may seem glacially slow, but over a few years, extraordinary. We can do this!
The young particularly are driving action, such as Greta Thunberg who started the movement of school striking children in Sweden, by standing outside the Swedish parliament.
Greta Thunberg. August 2018, as she started her school strike for the climate
Here is her emotional speech to EU leaders.
Longer video here
She is speaking at a critical time. As part of the Paris agreement, countries are expected to increase the ambitions year on year. The EU is already better than 3 °C compatible but not yet 2 °C compatible, however its ambitions can make it 1.5 C compatible it if goes through on them. Amongst those listening, as you can tell from the questions, many are in support of her. Climate change is likely to play a major role in the next EU elections this May. For a summary of how the EU is doing on climate change, see the EU page on Climate Tracker.
This is surely helping to motivate the governments to do more. However, there is much understandable fear, and even hysteria, in some responses, which doesn’t seem to be strongly based on science, and a tendency to use "Climate slogans" that are not always accurate, or are over simplified. As an example, the Extinction Rebellion are disrupting services throughout London right now, with the aim to get the UK government to commit to zero carbon emissions by 2025.
Government must act now to halt biodiversity loss and reduce greenhouse gas emissions to net zero by 2025.
But where does that figure come from? They don't say, I've looked on their website and there is no explanation of it anywhere. It isn’t in the 2018 IPCC report which says we need to reach that level by 2050 for the 1.5 °C goal.
I’d like to focus in this article on what the climate scientists themselves say. Also on what we are already doing, and what they say we need to do in the future.
This is another article I'm writing to support people we help in the Doomsday Debunked group on Facebook , that find us because they get scared, sometimes to the point of considering suicide, by such stories.
You can see this blog post with a table of contents on my website:
Add table of contents to this page (on my website) - blog post on Science 2.0 without the TOC
There’s a pervasive idea in our society of an almost impossible situation, that we can’t do anything about climate change, or that nobody is doing anything, or that we are headed for a doomsday scenario and it is almost over, already. None of that is true, not remotely so.
, a lead author for the IPCC report in 2018, spoke out about this in : Why protesters should be wary of ‘12 years to climate breakdown’ rhetoric in The Conversation:
Today’s teenagers are absolutely right to be up in arms about climate change, and right that they need powerful images to grab people’s attention. Yet some of the slogans being bandied around are genuinely frightening: a colleague recently told me of her 11-year-old coming home in tears after being told that, because of climate change, human civilisation might not survive for her to have children.
In Doomsday Debunked we encounter young kids like this all the time, scared sometimes to the point of being suicidal that they will not live to adulthood, and young adults who feel they shouldn't have children because they have read that they would be bringing them into a future uninhabitable Earth. A fair few are receiving therapy and drugs to treat PTSD and GAD and other anxiety disorders, and have panic attacks and vomit in fear many times a day out of fear of an uninhabitable Earth as well as other nonsense such as the constant fake NASA asteroid warnings in the sensationalist press. The sad thing is that much of what scares them so much is out and out junk science, exaggerated stories or these over simplified climate slogans.
Myles Allen continues:
The problem is, as soon as scientists speak out against environmental slogans, our words are seized upon by a dwindling band of the usual suspects to dismiss the entire issue.
Even when the climate scientists do speak out, as they do sometimes, their views do not get the publicity - a story is far more likely to be shared on social media or run in the mainstream news if it says that all the insects will die, civilization end or humans become extinct.
There is much that does need climate action, and our situation is indeed serious in many ways. However none of the expert projections of the IPCC and others of a similar high quality are of an uninhabitable Earth or a literal collapse of civilization. Also though many individual species do risk extinction and are going extinct, when it comes to ecosystems, many are actually becoming more species diverse due to human effects, with new habitats and species brought in from other parts of the world. The corals are the only complete ecosystem highlighted as at risk of near extinction (see below).
Myles Allen,continues, in his : Why protesters should be wary of ‘12 years to climate breakdown’ rhetoric
Using the World Meteorological Organisation’s definition of global average surface temperature, and the late 19th century to represent its pre-industrial level (yes, all these definitions matter), we just passed 1°C and are warming at more than 0.2°C per decade, which would take us to 1.5°C around 2040.
That said, these are only best estimates. We might already be at 1.2°C, and warming at 0.25°C per decade – well within the range of uncertainty. That would indeed get us to 1.5°C by 2030: 12 years from 2018. But an additional quarter of a degree of warming, more-or-less what has happened since the 1990s, is not going to feel like Armageddon to the vast majority of today’s striking teenagers (the striving taxpayers of 2030). And what will they think then?
As he says the IPCC projections are the best estimates. They are based on review of the academic literature at the highest level, but they always have a range of uncertainty. He says that it's not impossible that we reach 1.5°C by 2030, that it's within the range of uncertainty, but this is not an uninhabitable Earth, or anything resembling it. If we do hit this level, the world will feel much as it does today to the majority of the population of the Earth. (The expected time to reach 1.5°C is between 2040 and 2050, but there is enough uncertainty so that 2030 is not impossible).
He goes on to say that "the IPCC does not draw a “planetary boundary” at 1.5°C beyond which lie climate dragons."
...
So please stop saying something globally bad is going to happen in 2030. Bad stuff is already happening and every half a degree of warming matters, but the IPCC does not draw a “planetary boundary” at 1.5°C beyond which lie climate dragons.Why protesters should be wary of ‘12 years to climate breakdown’ rhetoric - by
How many of you have seen or shared 's post Why protesters should be wary of ‘12 years to climate breakdown’ rhetoric ? I expect nobody.
How many of you have seen or shared that study that was on TV saying that we are headed for a world without insects in 40 years? Did you know that that study had only one data point for the whole of China, for the domestic honeybee? It's like using sheep in a study on declines of mammals. Most of the map is blank, and the few studies they do include come from a literature search for "DECLIN*".
This is what the insect ecologist Manu Saunders had to say about it in a tweet:
The key take-home is the amount of white space on this map of available data showing local/regional declines. Most countries have no data. N.B. the single data points in Australia & China are both managed honey bees, not wild insects pic.twitter.com/PNNlZ7yGaR
— Dr Manu Saunders (@ManuSaunders) February 3, 2019
Those purple bars in Australia and China are for the domestic honeybee
Yet nobody shared the much more thorough study from the UN released just a week later which concluded that the situation is mixed, some increasing, some decreasing and some stable, and also went into detail about the many measures being taken to protect insect biodiversity (see below).
Or you may heard that humans are going to go extinct in 2026. If so you have probably been duped by one of the "Arctic News" blog posts by Sam Carana. Widely shared on social media, they feature graphs that project a sudden increase of temperature by many degrees in a few years. You may have been deceived by the impressive list of "contributors" on his About page. Few bother to click through and discover that he credits every professor whose video he embeds in his daft blog posts. Most likely they don't even know that he has done this, as anyone can embed their videos under YouTube's license!
He uses a quadratic (or other polynomials) to extrapolate. You may see the absurdity if I extend his graph both ways in the blue inset below:.
Such a graph always decreases from an infinite temperature in the past and increases to an infinite temperature in the future - unless they decrease to minus infinity both ways (see below). Or what about Guy McPherson's blog posts and videos. Many are impressed because he used to be a professor, but sometimes professors lose their way, and fall into junk science. He uses Sam Carana's absurd "polynomial extrapolations" as one of his sources for his predictions, 'nuf said!
Or you may have heard of Jem Bendell's "Deep Adaptation", the paper that is "driving people to therapy"? It failed peer review, not for the views expressed, but because it didn't meet academic standards(see below). Or, "Uninhabitable Earth", the sensationalist book by the generalist journalist David Wallace Wells who has only been interested in climate science for two years (see below ), or the often repeated journalistic claim that the IPCC report said that the only way to stop global warming is a tax leading to $240 a gallon for fuel (see below)?
Or the claim of a runaway feedback from a "methane bomb" (see below), or from the Siberian Permafrost (see below), that our agricultural land is going to run out of topsoil in 40 years (see below), that nearly all species will go extinct this century (see below), or that the Amazon jungle will soon burn down and be gone (see below)? Or the 1972 "supercomputer" that predicted an end of civilization in 2040 (see below). Or Adam Frank's model that supposedly showed our civilization will end in one of three horrible ways (see below). Or perhaps you have heard that we are going to run out of oxygen to breathe (see below). Or that we risk a cascade of tipping points leading to a hothouse Earth (see below).
I expect almost everyone with an interest in the topic has come across most of those stories and more. You may be surprised to learn how much of that is based on misunderstandings, exaggerations, sensationalism, climate slogans, and junk science.
If only the journalists and bloggers would heed the warnings about climate slogans by scientists like Myles Allen. Some probably do. However, it would take some major change or initiative for all journalists to stop doing the click bait titles. For as long as some do, those ones get shared and rise in Google results. It would also take some major change to deal with this issue of the junk climate science widely shared in social media. Perhaps social media initiatives to flag fake news may help, but so far they don't do anything, share Sam Carana's blog and there is no indication at all that it is junk science. How can your average reader, with no physics background, know this? Meanwhile, the bloggers have freedom of speech. They are not doing anything illegal by publishing nonsense even if they know that what they say is false.
It is hard to know what to do when faced with what seems an onslaught of fake and exaggerated climate change news. Since the start of 2019 the pace has really heated up. Most weeks we get a virally shared fake or exaggerated climate catastrophism or climate slogan story on social media, and often click bait and exaggerated or mistaken items on the mainstream news or on mainstream TV too.
I do have a petition to Google News and other news aggregates, asking them to stop promoting fake and junk science news stories, and to journalists to be more responsible in their reporting, which you may want to sign and share, and any suggestions do say in the comments!
Meanwhile the main thing one can do is to tell the truth, as clearly and succinctly as one can. If you are a blogger or journalist, please do the same, and anyone - please do more sharing of the posts that present the true situation and less sharing of the junk science. Try checking a climate change story against reliable sources first. Our Doomsday Debunked group may help you, as we now have a fair few members with a decent scientific understanding of climate change.
Also, if you are a climate scientist or expert, you may like to consider joining our group and giving a bit of your time to help the scared people who constantly panic about climate change and other doomsday scenarios.
Anyway, I’d like to focus in this article on what the climate scientists themselves say rather than the climate action slogans. Also I will cover what we are already doing, and what they say we need to do in the future.
For instance, how many of you know that the EU reduced emissions by 22% from 1994 to 2017? It is on track to meet its 2020 target
Progress made in cutting emissions - Climate Action - European Commission
Its long term strategy is zero emissions by 2050, and if it achieves that, it makes it 1.5 °C compatible. The UK has done even better, see Slow burn? The long road to a zero-emissions UK. In the UK, our emissions are now the lowest since 1920. The government says greenhouse gas emissions have fallen by 42% since 1990. Greta Thunberg told MPs in Westminster that the true reduction was more like 10%. The reason is, the UK is using territorial emissions, which is the fairer way to look at a countries own work to tackle climate change. She is using the pattern of consumption, which includes effects from other countries for instance if we import from China, it would depend on their policies not ours, things that we can't do anything about (except by importing from someone else). It can also lead to some double accounting where the same figure is counted twice. The method the UK uses is the method adopted for the Paris agreement. See Climate change: Is Greta Thunberg right about UK carbon emissions?
China and India are often criticized because their emissions are still increasing. But they start off with much lower emissions per person, especially India with only 1.8 tons per capita well below world average of 4.2 tons per capita. They are rapidly industrializing, yes but they aim to achieve this without increasing emissions, indeed, to reduce emissions. It takes a while to turn around the energy use of a population of over a billion people so you can’t expect this to happen in just two years.
India remains on track to overachieve on its 2 C compatible target and 1.5 C is within reach India | Climate Action Tracker, see also Guest post: Why India’s CO2 emissions grew strongly in 2017 | Carbon Brief
China faces the biggest challenge of all, it is expected to meet its commitments which include 20% non fossil fuel by 2030 and to peak emissions before 2030 but it has to increase its commitments for us to have a chance to say within 1.5 C. China | Climate Action Tracker
Although the US has no climate change initiatives at the Federal level after Trump's declaration of his intention to withdraw from the Paris agreement, it has strong support at a subnational level. Initiatives already taken will bring it nearly halfway to its Paris pledge to reduce emissions by 26-8% by 2025, and subnational commitments and pledges will lead to a reduction of 17%, over two thirds of the way. The report by California governor Jerry Brown and UN’s special envoy for climate action Michael Bloomberg in 2017 outlined a roadmap to reach a 24 percent emission reduction by 2025 and make 26% achievable shortly thereafter. prepare for faster emission reductions beyond 2025. See Fulfilling America's Pledge.
Cities and other non state actors also have an important role. In the UN review published ahead of the Global Climate Action summit in September 2018, they found that pledges by non-state actors represent a global reduction of between 1.5 and 2.2 gigatonnes of carbon dioxide equivalent by 2030. But the combined effects can be much larger. Erik Solheim said:
“Cities, states, civil society and the private sector can be the resource that puts the world over the top in our fight to reduce CO2 emissions,”
The 2018 Yale study found that there is a lot of potential in these subnational initiatives. Indeed they concluded that if they are all fully implemented along with the NDC's (Nationally Determined Contributions at the country .level), and taking account of overlaps, that we can already reach our 1.5°C goal! Not that they necessarily will all be fully implemented, but this shows the vast potential there is at the subnational level.
In summary, Angel Hsu, Director of the Data-driven Yale said:
“What our report shows is many actors are signing up to take actions, but their ambition and ability to move us faster and closer to reach the Paris climate goals in time is limited. What’s needed now is the financing, policies, and support to urgently realize these efforts.”
As far as I can see the demands of the Extinction Rebellion are not based on any report by climate scientists. By pushing for nearly impossible demands they risk a future where we commit to things that we can’t achieve, instead of committing to things that are possible.
The thing that has made the Paris agreement such a success is that nations are able to set policies they know they can achieve at every stage, and then increase their pledges year on year as they gain experience and develop new industries to make it all possible. I think we need to continue in the same spirit. Be ambitious, but make sure our goals can be achieved when we commit to them.
The UK government’s plan is to reduce emissions by 80% in 2050. That’s not enough yet, but if it steps up in its pledge to a 100% reduction, it would then be 1.5 °C compatible to save the corals UK steps towards zero-carbon economy. This is something we can pressurize them to do. And then to be even more ambitious once they do that.
According to the IPCC report in 2018, we lose 99% of the corals after just a decade or so at 2 °C, and the reefs probably do not recover. If we don’t go much above 1.5 °C then 10 - 30% of them remain and they can recover, though this may take a long time. They can recover because they can adapt to warmer temperatures, as well as migrate and set up reefs in places that used to be too cold for them, but at 2 °C the warming is too rapid for this to work so well.
They do caution that these projections are not certain and that it’s possible that corals are more resistant than this, or that we can do things to help them adapt. See box 3.4, page 230 of their chapter 3.
They found that no other major ecosystem on Earth is so sensitive, either in the sea or on land. The corals are the only entire ecosystem we risk losing at 2 °C. Humans for sure are not at any risk of extinction under any of the scenarios,
There is a risk of severe impacts on other ecosystems however. In this map the regions marked in red risk severe impact at 2 °C, and the dark red regions, at 1.5 °C.
Figure 3.16 of chapter 3 of the IPCC report in 2018.
The coloured regions highlight risks of sever impact. The gray scale regions correspond to moderate impacts at those various temperatures.
This doesn’t mean that the ecosystems vanish. Rather, they change to other ecosystems. For instance the melting permafrost will lead to a radically different ecosystem in northern Canada, Alaska and Siberia, in a 2 °C warmer world, but this warmer world would be more habitable for humans in the far north, with far more vegetation, and letting us grow crops using conventional agriculture that never could grow there before. The pace of the change is the main issue.
It is important to stay within 1.5 °C for these and many other reasons. However, our future is a habitable world for humans in all the scenarios. Indeed it has been greening as a result of the CO2 fertilization effect so far (Rising CO2 has 'greened' world's plants and trees | Carbon Brief). This should continue through to 2050 at least, with increasing crop yields, and faster growing trees (see below)
It’s the transition, and the speed of transition that matters, far more than the end state. Even at an increase of 12 °C then the world is still very habitable for humans, as we’ll see. What’s more we have already averted a possible ice age 20,000 years from now, and are headed to a future where there won’t be any ice ages for hundreds of thousands of years. That is good because interglacials are far more stable than ice ages when there are often wild swings in temperature.
The IPCC do project tens or hundreds of millions of climate refugees and other serious effects at 2 °C of warning. At that temperature point, we may get population densities quadrupling in some places in the sub tropics due to the migrants from the tropics.
That is a serious societal impact in anyone’s books. However, there is nothing in the report about collapse of society or an end of civilization. Those “predictions” are all embellishment by journalists, which sadly are often just believed “as is” by their readers, especially young children.
Here is what they say about climate migrants in chapter 3:
Displacement: At 2°C of warming, there is a potential for significant population displacement concentrated in the tropics. Tropical populations may have to move distances greater than 1000 km if global mean temperature rises by 2°C from 2011–2030 to the end of the century. A disproportionately rapid evacuation from the tropics could lead to a concentration of population in tropical margins and the subtropics, where population densities could increase by 300% or more
page 245, 3.4.10.2 The changing structure of communities: migration, displacement and conflict from chapter 3 of the IPCC report in 2018.
This summary table shows the numbers affected at various temperature increases. We are currently headed for 3 °C, the last column,
Figure 3.4 page 246 of chapter 3 of the IPCC report in 2018.
Habitat degradation and crop yield change are particularly vulnerable to the difference from 1.5°C to 2°C.
The situation is undoubtedly serious. However, it is remarkable what we have achieved and are achieving, and can do in the future, especially when you look back to before the Paris Agreement in 2016. Back then admittedly things were dire. The earlier Kyoto protocol agreement based on carbon trading was a flop, leading to only modest commitments.
But then we had this truly major breakthrough.
What you need to know is that the Paris agreement only came into place in 2016. They agreed the rulebook for the first time in December 2018, an essential step before implementing it properly.
When the US decided to leave, this made only a small dent. Indeed Trump may well have galvanized the other countries into more action as well as many cities, companies, states and individuals in the US itself.
In two years, worldwide, we have already implemented policies to knock an entire degree off the temperature projected for 2100 from around 4 °C to around 3 °C.
This shows what we can do if we work together. If we keep up this momentum for the next decade, who knows what we can achieve? Might we not be able to knock another 1.5 °C off the projection for 2100 with our actions in the next twelve years? After all the whole idea of the agreement is that pledges increase year on year.
It is important to keep up the momentum. However, the IPCC made it clear in their report that 1.5 °C is scientifically possible, is affordable and is achievable. The main thing required is the political will to do it.
You so often hear that politicians are not doing anything. This also is not true. Some countries already target below 2 °C. The most populous of those is India, with a population of 1.339 billion, not far off that of China.
It is not far from achieving a 1.5 °C compatible target according to Climate Action Tracker.
Populations of India, China and the World showing how India's population is not far off that of China now. Using World Data via Google.
That is a substantial chunk of the world population that is already well on its way to 1.5 °C. Many of the smaller countries are doing even better and are already below 1.5 °C compatible. For more on this see below.
The journalists just about always hopelessly exaggerate the IPCC reports and add numerous embellishments. Even the mainstream news, such as the New York Times, have their share of exaggerations and misinformation.
A good example here is the mistake the New York Times made about carbon pricing. They confused the future mitigation costs of sea wall defences, of climate migrants, etc with the incentive tax to prevent emissions of that CO2, as part of an integrated program. The mitigation costs could rise to $27,000 a ton by 2100, but the aim of a carbon pricing incentive tax is to prevent us getting into this situation at all. This is estimated at various values of $5 upwards, as part of a mixed program of many measures. If this succeeds, then of course we never have to pay the mitigation costs.
They weren’t the only ones to make this mistake. The Hill also ran a story based on this claiming that the IPCC was saying that gas (petrol) would cost $240 a gallon
This is such a major misunderstanding. The passage they got the figure from is crystal clear, if you are used to reading scientific papers. It’s hard to know how the confusion arose. But this is just one of many confusions in even the mainstream press. Instead of going by what the co-chairs said, the journalists went through the report, misread a few passages, and riffed on their misunderstandings without running them past anyone.
Another major misunderstanding was the claim that the IPCC pathways required vast amounts of CO2 sequestration using technology we don’t have yet. Far from it. The pathway to zero emissions by 2050 only has a practical amount of reafforestation as a carbon negative measure, to offset a small part of the emissions. From the technical summary:
“The overall deployment of CCS varies widely across 1.5°C pathways with no or limited overshoot, with cumulative CO2 stored through 2050 ranging from zero up to 300 gigatons CO2 (minimum–maximum range), of which zero up to 140 gigatons CO2 is stored from biomass”
For more on this see Four ways to get to 1.5 °C (below)
The NY Times title was also click bait: “Major Climate Report Describes a Strong Risk of Crisis as Early as 2040:”. That possible crisis was for coral reefs as early as 2040, not for humanity.
Also, the central message of the report was that this can be averted with policies to stay within 1.5 °C, and that this is scientifically possible, affordable and just needs the political will. That is the positive side of the report which was not highlighted in headlines, and barely mentioned in the articles either.
Try watching the videos by the co-chairs and the press conference for the IPCC report in 2018
Watch the original press conferences and compare with the New York Times report, and others in the mainstream press at the time, and you wonder if they went to the same event.
Climate activists and journalists often make a big deal of this, giving the impression that our climate policies can’t be working for as long as we have increasing emissions.
Yes, our yearly CO2 emissions are still rising, but that’s not surprising. After all China and India are rapidly industrializing, and though they are transitioning to green energy as they do so, and their emissions should peak before 2030, the year on year emissions are not likely to come down much before this happens.
All the scenarios project a rise for at least a few more years, even the ones with 1.5 °C targets. If we keep to our current policies and unconditional pledges, this will turn this around to a phase of year on year reduced emissions within a few years.
Also, that's just the start. We should expect CO2 levels in the atmosphere to keep increasing long after our yearly emissions start to reduce. It is only when the emissions reach zero, that our CO2 levels and temperature stabilizes. Even with the 1.5 °C compatible paths, this doesn’t happen until the mid century.
With current policies and unconditional pledges we are headed for around 3 °C with a 2/3 chance of staying within 3.2 °C (see summary graphic). That’s just a start. We are bound to get to lower targets than that as they ramp up the pledges.
The bloggers and journalists who share graphs and say “look, we haven’t achieved anything yet” are looking at them with the wrong kind of analysis. This is not a reason to be disheartened.
Many of the journalists reported that we have a decade to avoid disaster, and the more sensationalist accounts say that we risk human extinction, within a decade.
That’s not what the IPCC said. It was widely misreported and I think the journalists have a lot of the responsibility for the current hysteria, due to the way they mislead the public by not summarizing what they said accurately.
The report actually said that the best way to 1.5 °C is to reduce CO2 emissions by 45% by 2030.
C.1. In model pathways with no or limited overshoot of 1.5°C, global net anthropogenic CO2 emissions decline by about 45% from 2010 levels by 2030 (40–60% interquartile range), reaching net zero around 2050 (2045–2055 interquartile range).
Technical summary:
Limiting warming to 1.5°C depends on greenhouse gas (GHG) emissions over the next decades, where lower GHG emissions in 2030 lead to a higher chance of keeping peak warming to 1.5°C (high confidence).
Available pathways that aim for no or limited (less than 0.1°C) overshoot of 1.5°C keep GHG emissions in 2030 to 25–30 GtCO2e yr−1 in 2030 (interquartile range). This contrasts with median estimates for current unconditional NDCs of 52–58 GtCO2e yr−1 in 2030.
...
In model pathways with no or limited overshoot of 1.5°C, global net anthropogenic CO2 emissions decline by about 45% from 2010 levels by 2030 (40–60% interquartile range), reaching net zero around 2050 (2045–2055 interquartile range). For limiting global warming to below 2°C with at least 66% probability CO2 emissions are projected to decline by about 25% by 2030 in most pathways (10–30% interquartile range) and reach net zero around 2070 (2065–2080 interquartile range).Technical summary, page 33 of the full report.
So, we have twelve years to reduce emissions by 45%. Nothing much will happen in 2030. But unless we are already down to a 45% reduction by then, it will become increasingly harder to remain within 1.5 °C by the middle of the century.
After that we reduce to zero by 2050.
That’s for the 1.5 °C pathway. If we want to stay within 2 °C then it’s much easier. For that pathway, we need to reduce 25% by 2030 and reach net zero by 2070.
Also, reaching zero emissions by 2050 (or 2045) was only one of four ways to stay within 1.5 °C. We can also overshoot a little (not all the way to 2 °C), and then use negative emissions to get back again.
But the easiest, the first of these pathways, has no carbon sequestration. The area shown in brown is reafforestation:
Global Warming of 1.5 ºC - chapter 1, figure 1.4
Even if we don’t manage that, and the temperature briefly reaches 2 °C, it is possible to get back down to 1.5 °C if we remove CO2 for the rest of the century to compensate.
That needs carbon sequestration shown in yellow, starting around 2050 in the other three pathways.
From the IPCC technical summary
“The overall deployment of CCS varies widely across 1.5°C pathways with no or limited overshoot, with cumulative CO2 stored through 2050 ranging from zero up to 300 GtCO2(minimum–maximum range), of which zero up to 140 GtCO2 is stored from biomass”
This is existing technology. The plant in Abu Dhabi pumps 800,000 tons of CO2 a year into old oil reserves, a byproduct of iron and steel production, used for enhanced oil recovery. They plan to expand to capture 2.3 million tonnes per year by 2025 and 5 million tonnes per year before 2030. The one in Petra Nova captures 1.4 million tonnes a year from a coal fired power station - so is an exact analogy of the biofuels carbon capture and storage. Both are used currently for enhanced oil recovery where the injected CO2 is used to
The Sleipner gas fields CO2 injection in Norway alone can store 600 billion tons. That alone is enough to store all the CO2 for even the fourth of their paths, so there is no problem storing it if we can pipe it to suitable reserves, which are also present in many places. For instance the UK also has billions of tons of storage potential (CO2 Storage in the UK-Industry Potential - 2010.).
The main issue is the amount of land would be used to grow al those trees for the powerplants that use biomass.
This shows conceptually the idea of the two approaches. The best approach is the one to the right,
This is a good summary of some of the main points in the agreement:
See also 3.4. Four ways to get to 1.5 °C (below)
And - this is hardly utopian as a vision. We have done so much already. This graph gives an idea of what we have done already. Our current policies are already well below the “no climate policies” orange region. Remember most of this has been achieved in only two years!
We have another ten years to get onto the 1.5 °C track. First we need to stop our current increase in CO2 emissions year on year, then we need to do the 45% reduction which is the start of the easier P1 pathway. We can definitely do it. That was the conclusion of the IPCC report. It’s a matter of politics, not science, whether we do this.
Of course the US plan to withdraw. But they are not the largest emitter, China is, and they are the most important of all to reduce quickly. They are responsible for half of the extra emissions that caused emissions to rise again in 2017 after plateauing for a couple of years.
There the bars show the increases or decreases. As you can see half the increase from 2016 to 2017 is from China. Graph from here:
As we’ll see they are fulfilling their pledges under the Paris Agreement - which is not to stop increasing yet - they only committed to peak some time before 2030. But that much is really ambitious for a rapidly industrializing country and they seem on track to do it. We need more ambitious pledges from them to stay within 1.5 °C. But they have fulfilled their pledges so far.
They have a strong incentive as they are amongst the most affected.
With “business as usual” then parts of China would get so hot that farmers can’t work in their rice fields any more during heat waves, and coastal cities are vulnerable to flooding. So, they are very motivated to do something about it. Also, as major contributors to the carbon emissions they are also in a position to be able to make a big impact on climate change just by themselves. See this graph:
Graphs from: CO₂ and other Greenhouse Gas Emissions
Within the US too, then there is strong support for the Paris agreement in many sectors
The United States climate alliance accounts for 16 states, as well as the territory of Puerto Rico committed to upholding the Paris agreement within their borders. Amongst those sixteen, California if they were a separate country would be the fifth largest economy in the entire world.
Major cities around the world have committed to build only zero carbon buildings by 2030 and to make existing buildings zero carbon by 2050. In the US that includes New York City and San Francisco:
New York which has 60% of the California economy.
And the US may well return to the Paris agreement in the future at some point before 2030. Trump could change his mind, and the next president in 2022 or 2026 may well return to it, especially with increasingly clear symptoms of climate change and its effects in the US. That is time enough for the US government to join in reducing emissions to zero by 2050.
And remember most of this has happened in the last two years. So how much can we achieve in the next ten years?
You can watch it here: Attenborough presents Climate Change - The Facts
It may sound frightening, but the scientific evidence is that if we have not taken dramatic action within the next decade, we could face irreversible damage to the natural world and the collapse of our societies. We are running out of time but there is still hope. I believe that if we better understand the threat we face, the more likely it is that we can avoid such a catastrophic future" Attenborough climate show a 'call to arms'
This is another example of climate change slogans. Strictly speaking it is not literally true. The IPCC report did not say we have to take dramatic action in the next decade. They said that immediate action is the easiest way ahead, scientifically feasible and affordable, and that there are increasingly more dramatic measures needed if we postpone action. The IPCC report also says nothing about societal collapse, at least not large scale collapse.
David Attenborough's program focuses on local communities severely impacted by climate change such as the climate migrants impacted by flooding and those whose houses burnt down in the California fires. In that sense it is a collapse of local communities, which will become much more widespread in a warming world. That may be what he meant. On a larger scale though, we have a lot of climate change resilience. There is also much work being done on increasing that. For more on the research into climate change resilience (see below)
Before getting to more details about climate change, I’d like to debunk some of the popular misconceptions. There are many stories you may have read and believed that are just false.
Here is a YouTube video of some young women who are so scared that they feel they can't bring a child into the world, and as I said in the intro much of what scares the general public is false or junk science.
I will start with one of the most widely shared, a junk sociology paper that failed peer review, that climate scientists say is just "crap" but is widely believed by the general public.
Many have been scared by Jem Bendell’s “Deep adaptation”. He is a sociologist who relies extensively on Wasdell’s never published non peer reviewed article. This in turn depends on the now disproved Clathrate Gun Hypothesis.
This is the article that is supposedly so depressing it’s driving its readers to therapy. I can well believe that this happens, from the panicked and scared PM’s I get. But the article itself is grounded in junk science. That it makes people depressed doesn’t mean it is correct.
The distinguished climate scientist Michael Mann, director of the Earth System Science Center at Pennsylvania State University had only one word in comment. Just four letters “Crap”. See the other responses to his tweet too. His tweet is here.
— Michael E. Mann (@MichaelEMann) March 6, 2019Later in the conversation he amends this to"Hogwash", tweet here.
Sorry, Hogwash ...
— Michael E. Mann (@MichaelEMann) March 6, 2019
I cover this in detail in my article:
Others have been scared by this article and then book by David Wallace-Wells. He doesn’t write like a scientist. He says himself that he is a general journalist who has only been interested in climate change for one to two years.
His book is just a scrap book of the scariest stories he has found, not a systematic survey. He misunderstands things, exaggerates, and misses important nuances in the stories he covers.
The evidence that climate change is a serious problem that we must contend with now, is overwhelming on its own. There is no need to overstate the evidence, particularly when it feeds a paralyzing narrative of doom and hopelessness. I'm afraid this latest article does that. That's too bad. The journalist is clearly a talented one, and this is somewhat of a lost opportunity to objectively inform the discourse over human-caused climate change.
For more about this see my:
These are fake news stories. One of the worst of the junk blogs is:
He uses quadratic equations, and other polynomials to project! An utterly bizarre idea to a mathematician.
This image may be enough for you to see how ridiculous his posts are. In the blue inset I have extrapolated his quadratic (or one very close to it) both ways so you can see how it will always predict an increase to infinity in the future and decrease from infinity from the past (unless it’s the other way around, increase from absolute zero and decrease to absolute zero) - it is a RIDICULOUS way to extrapolate.:
Another one here
From: How long do we have?
To back up his nonsense he does stuff like this,
There is no basis for it - it's all make believe. In his diagram on that page he says that between 2025 and 2026 there will be a sudden 8°C increase in temperature due to "cloud feedback". That's not based on any science. Just that he needed some gobbledygook to put in his graph to add a sudden 8 C because that's what his polynomial does.
Presumably it's meant to be about the cloudless skies study, which is based on CO2 levels of 1400 to 2200 ppm, a level we can't reach until the 22nd century even with business as usual. It is not even remotely relevant to the conditions we are in right now in (see below).
If we instantly stopped anthropogenic emissions then it would lead perhaps to a bump by 0.15 C for 20 years.(see below), The "methane bomb" is disproved (see below), and the Siberian Permafrost effect is minute for this century on the path we are on (see below)
This blog sadly impresses readers because the credentials of the “contributors” on his deceptive About page seem impressive
It goes on and on, 33 contributors, professors and emeritus professors.
However, click through to the linked names on his About page, and you realize he will credit as a “contributor” any of the people talking in embedded YouTube videos in any of his blog posts. He surely hasn’t asked permission of any of them and there would be no reason for them to even know that the video is on his blog. He just includes this material under the YouTube license for embedding content. Others are included because he quotes a short paragraph from them, or includes an article they released under a creative commons license.
Sadly many people do believe his blog, at least partly because they believe the About page and think he must have something going for him to attract posts from so many distinguished professors. Just nonsense!
The other junk scientist who scares many people is
You can tell how far he has gone in the direction of junk science when you discover he uses Sam Carana’s blog with its daft polynomial projections as a source for his own predictions!
Guy McPherson keeps saying the average temperature of Earth is going to increase rapidly by several degrees in a few months. None of it ever happens because it is based on junk science like this.
You are not at risk of extinction in any of the climate scenarios. The worst that happens is that the world gets so hot perhaps you start to grow coconuts in the Mediterranean and oranges in the UK. Not that you have coconuts growing in Canada or that humans can’t survive at all.
This is a computer program that simulated the world as five numbers for everything. In 1972 it needed a computer that filled a room. Today it would run in a fraction of a second on your mobile phone.
It is just a coincidence. It predicted the number of children would stop going up because we could no longer find the resources needed to bring up children any more by now. But it's the opposite.
The number of children is almost the same as it was a decade ago, that’s true.
However, it is because we have food and other resources for our children, and have good medicine to prevent children dying and as a result people are having fewer children worldwide. It is in a background of greatly increasing life expectancy. Ten to 20 years in the last 50 years.
See
Here is a graph from that page:
The countries with decreasing populations are places like Japan which have a the highest standards of living.
Japan Population | 1950-2018 | Data | Chart | Calendar | Forecast | News
All this is the opposite of what their model predicted, fewer children because of poverty and not being able to bring them up, and a situation of scarcity and hardship, and short lives.
It is just a coincidence.
We should use the UN population division and other modern well tested and thoroughly researched projections and modern computers and programs not this ancient 1972 program that uses only 5 numbers to represent the entire world!
My article about it is here:
Debunked: No we are not on track for end of world by 1972 computer model
This is another similar one
From appendix D they have a parameter W for wellbeing and they assume that as the well being of a population increases the population growth rate increases, becoming superexponential. That would seem sensible from studies of animal populations. But humans don’t do this.
As our well being increases our population has leveled out. The opposite of what their model suggests. We have already almost reached peak child, we are living a lot longer, and our birth rate has gone right down, to less than replacement in some of the wealthiest countries such as Japan which already has a declining population.
The only major region of our world which still has a high birthrate is the least prosperous, Africa. As it becomes more prosperous with better health care, higher education particularly of women and reduce child mortality its birthrate is expected to fall down to around 2 children per family, as parents become more confident that their children can survive to adulthood and be healthy.The population is expected to level off also. Our final world population depends a lot on how rapidly Africa develops towards these conditions of higher education, reduced child mortality, better health etc.
When will the world reach 'peak child'?
A sociology author has used this simple model, which doesn’t match what is happening to us, to predict that society would collapse. On the science, he says to find out more to read David Waltham's book, which is awful. My debunk of it is here
Quoting from his article:
"The continued growth for much of this period, as well as the very slowly decline in the latter part, is mostly due to the increasing birth rate. Only after a few decades, when the world is approaching global societal collapse, does the death rate overtake the increasing birth rate. … In the present situation, famines tend to be very local problems as much of the planet can import food in case local production is insufficient, but this won’t be the case in a world in which food shortages are no longer local but worldwide (and in which global trade is breaking down)."
But the fundamental premise there is flawed, there isn’t an increasing birthrate. It is decreasing rapidly worldwide.
This is a first paper in what they hope to be a long term study. It’s an interesting project, but it should not be used to predict what will happen to Earth in the future.
Their research is at far too early a stage to be relevant to any of that. It makes many simplifying assumptions that do not apply to Earth as it is now. But their aim wasn't to predict what would happen to Earth. It was to try to get a general picture of what can happen to all possible exoplanet civilizations. A huge project that they are just making a start on.
First, let's look at some of its simplifying assumptions - none of which apply to our Earth (no surprise)
So, what is actually going to happen to Earth?
What could happen even longer term?
They never claimed any direct relevance to Earth and expect future studies to be more detailed, exploring the range of futures for extra terrestrial civilizations. As they do so, perhaps they may find trajectories resembling the one we ourselves are on, but at present it is just too simple a model to apply to Earth.
For more on this see my
The article is mainly about things that could happen centuries to thousands of years into the future. It doesn't really conflict with the IPCC who have already concluded that these tipping points may have significant but probably minor effects before 2100 - because it is a meta study and it is just looking at ideas for future research. There are no dates in it, and there is no new fundamental research.
The press release didn’t give timescales, and many of the news stories just riffed off the press release, and the authors don’t read the paper itself. When you read the paper, they still don’t give timescales, but it becomes clear that for most of this, they are talking about things that could happen over centuries to millennia.
They are not conflicting with the IPCC, which does climate projections mainly through to 2100. It is more that they are looking at a much longer future timescale.
Also, they don’t have any proof, and no new data or research, it’s more like a “meta study”, a result of looking at many other papers and then drawing up a hypothesis for other scientists to study. As they say in their conclusion:
Our initial analysis here needs to be underpinned by more in-depth, quantitative Earth System analysis and modeling studies to address three critical questions. (i) Is humanity at risk for pushing the system across a planetary threshold and irreversibly down a Hothouse Earth pathway? (ii) What other pathways might be possible in the complex stability landscape of the Earth System, and what risks might they entail? (iii) What planetary stewardship strategies are required to maintain the Earth System in a manageable Stabilized Earth state?
Indeed there is not a single future date in the article. It is all qualitative. The diagrams in it are just sketches with an arrow indicating time - but no markers along the time axis of centuries or millennia. It isn’t really adding anything new over the previous studies. It is more of a meta study.
This is one of their diagrams:
They are saying there are things we can do in the next couple of decades that can get the Earth into a good state, one in which it will neither get too hot nor too cold for hundreds of thousands of years.
They call this “Earth System Stewardship”. We are currently in that "Stabilized Earth" region of the chart.
If we stay well within 2 C, which is the ideal target of the Paris agreement, to stay within 1.5 C, then we are good for hundreds of thousands of years into the future, to have a stable temperature without the huge fluctuations of the ice ages.
However they say we are at a kind of decision point where the things we do for the next several decades could tip us into the “Hothouse Earth” cycle. That then could lead to Earth getting a lot hotter centuries to more like thousands of years into the future. Other scientists are skeptical of this report. It is not proved and there are no actual future dates in the article. It is all qualitative about things that might happen, mostly centuries to millennia into the future.
It has good news however. If we do manage to avoid the higher “business as usual”, which we are already doing, we have also avoided the next ice age too, and we are headed for the optimal “stabilized Earth”.
So, this is good news for future generations. So long as we manage to avoid excessive temperature rises, we can avoid the hothouse Earth and even thousands of years into the future our climate will be stable.
See my
Also see later in this page, Next ice age - postponed.
No not true at all.
There is plenty of oxygen in the atmosphere for many thousands of years and so there is nothing to worry about of that nature.
It’s not only us that will be fine. There is enough oxygen there for all the animals in the world to breathe for the foreseeable future even if, impossibly, photosynthesis ceased completely world wide. This is also taking account of all the natural processes that remove it. We are fine for oxygen for thousands of years no matter what happens.
This featured as main story on the TV with a claim that we risked all insects vanishing in 40 years.
But this is not true at all. It is a case of low quality research with a dramatic and scary conclusion being promoted through the roof by the press, and high quality research with the opposite conclusion quietly ignored or not even noticed.
This research was immediately criticized by ecologists. It was a not a systematic survey for one. The researchers just did a search for articles with “declin*” in the title, so of course they mainly found articles about declining populations.
They also found very few studies outside of Europe and the US. For the whole of China and for Australia the only articles they found were about honey bees, a domesticated insect. This is like including reports of declining numbers of sheep in an article on declining numbers of mammals. Most of their world map was a complete blank.
Those purple bars in Australia and China are for the domestic honeybee
There were some points in it of interest to academic readers who knew how to evaluate its limitations, but it should never have got so much publicity.
A week or so later the UN biodiversity in agriculture report came out. Their section on insects was systematic and thorough, based on sent in reports by experts in many countries reporting to the UN found a mixed picture. Some stable, some with mixed trends. Some countries reported increases of pollinators, such as Nepal, and also parts of Europe due to a policy encouraging flower rich field margins.
They reported that the German study, which found decreased insect numbers in nature reserves had lead to a new organization to do something about it. It is probably due to insecticides and agricultural practices reducing field margins, so there is much one can do.
The only habitats they identified with a significant decreasing trend in insects worldwide were for pastures grazed by livestock.
We can pollinate the few crops that need pollination using domesticated insects such as honey bees and the tropical “stingless bees”. But wild insects add to the diversity and increase crop yields. They reported on many projects to help improve pollinator diversity.
More on this later (see below).
This is not true. It was a theory due to James Hansen, who though he is a climate scientist, has a reputation of exaggerated statements about climate change. He published this idea, without any calculations to back it up, in a popular book with no peer review. He did not cite any published work on the subject in is book. Stephen Hawking also believed this and promoted it in an interview with the BBC.
It was soon disproved, as soon as the theorists set to work to run the calculations carefully. To do that we would have to burn ten times the total reserves of oil, gas and coal in the world.
More on this later (see below).
The methane has been leaking for millions of years, since before there was ice in the Arctic. The warming temperatures only affect the top 1.6 meters which are indeed very slowly destabilizing, in summer months only, and they are not able to contribute significantly to global warming.
More on this later (see below).
The extra albedo from ice melting there has a feedback effect locally, leading to more ice melt in summer than otherwise, but not globally. Also this is sea ice, floating on the sea, and it melting makes no difference to sea levels worldwide. This is taken account of in the models used by climate change and is a minor effect. There was a mistaken report said that depending on the scenario the Arctic has 5 to 9 C locked in if we meet the Paris agreement 1.5 C. It should have said 0.5 to 9 C. Was a typo. Factcheck: Is 3-5C of Arctic warming now ‘locked in’?
In Permian times the poles were ice free. Yes. But the Earth looked very different with no land locked Arctic ocean and no Antarctica at the south pole either. Earth at the time of the Permian / Triassic extinction
Ice ages like we have now normally happen when there are land masses or enclosed oceans at the poles. So you wouldn't expect it to have ice at the pole anyway even if it was as cold as us, it probably would have ice free polar regions, not just have an ice cap floating in open ocean with no land anywhere near - and it was also a lot warmer for other reasons, not fully understood yet. So it's just not valid to infer that because the poles were ice free in the Permian they will be for us. Antarctica doesn't melt totally for many tens of thousands of years under any scenario. Greenland could become ice free under "Business as usual" after a thousand years but for any other scenario
It's a result of something else, us warming the climate, then a bit extra added. Not a runaway. And it can go both ways on the 3 °C pathway we are on now. It could be a carbon sink through peat and vegetation growing. We can also encourage vegetation to help make it more carbon negative by irrigation. On our present pathway, the range of CO2 emissions is enough for something between a temperature rise by a small fraction of a degree by 2200 and a temperature drop by the same amount, most of it after 2100 (both less than a tenth of a degree total).
More on this later (see below).
The sensationalist press make a lot of this, that there are some effects that are not included in the models such as the Arctic permafrost. What they ignore is the reasoning that gives justification for leaving them out.
In a systematic review by the Royal Society they concluded that there are no known runaway effects. Nothing that acts like a gun or bomb. Yes, if we warm the climate and that can lead to some additional warming over long timescales. But nothing that exhibits “threshold behaviour”.
I go into all of these in more detail with cites in the section DELAYED EFFECTS (below)
The IPCC say that whenever we stop CO2 emissions, if we ramp down all the way to carbon neutral, then whatever temperatures we reached by the, those are the temperatures we are at from then on apart from a fraction of a degree (perhaps 0.15 C)
This said, in the summary for policy makers, that anthropogenic emissions so far have contributed 0.8 to 1.2° C since pre-industrial and that the emissions so far have will have effects that last for centuries to millennia, such as sea level rise and associated impacts, but these are unlikely to cause even a long term global warming of 1.5°C (medium confidence) and that with high confidence this is not possible over the next few decades. This is the figure they use to illustrate it: Even the purple path with no reduction in non CO2 radiation forcing (such as methane emissions and soot) doesn't have any increases or tipping points.
A.2. Warming from anthropogenic emissions from the pre-industrial period to the present will persist for centuries to millennia and will continue to cause further long-term changes in the climate system, such as sea level rise, with associated impacts (high confidence), but these emissions alone are unlikely to cause global warming of 1.5°C (medium confidence). (Figure SPM.1) {1.2, 3.3, Figure 1.5}
A.2.1. Anthropogenic emissions (including greenhouse gases, aerosols and their precursors) up to the present are unlikely to cause further warming of more than 0.5°C over the next two to three decades (high confidence) or on a century time scale (medium confidence). {1.2.4, Figure 1.5}
There may be some temperature rise “baked in” as a result of the masking effect of SO2 aerosols from coal burning and the like, which cool the planet down slightly, but if so, it’s only a fraction of a degree, around 0.15 °C and if we stop the CO2, and remove the black soot (which has a warming effect) at the same time as we reduce the SO2, we can prevent even that.
From: power point presentation by Professor Myles Allen. Based on Global Warming of 1.5 ºC - chapter 1, figure 1.5
If we stop all aerosol emissions, yellow line, there is a short term bump in temperature by 0.15 degrees, and returning to the previous temperatures in 20 years and ending with a reduction to 0.2 °C below the present by 2100
Temperatures go down slowly as soon as we reach carbon neutral, depending how you define carbon neutral.
If you define carbon neutral as continuing to produce enough CO2 to exactly match the natural negative emissions from all CO2 sinks including the sea, then temperatures stay more or less level, rising slightly, the blue line. If it means a net zero anthropogenic emissions they go down because the excess CO2 in the atmosphere is gradually removed over time by natural processes, with the yellow and purple lines.
According to Climate Action Tracker our current policies keep us within 3.3 °C, while the unconditional pledges and targets keep us within 3. 0 °C with a 66% or greater chance of remaining within 3.2 °C. This is their summary graphic
.
“In the absence of policies global warming is expected, to reach 4.1 °C – 4.8 °C above pre-industrial by the end of the century. ... Current policies presently in place around the world are projected to … result in about 3.3°C warming above pre-industrial levels. The unconditional pledges and targets that governments have made, including NDCs 2 as of December 2018, would limit warming to about 3.0°C above pre-industrial levels, or in probabilistic terms, likely (66% or greater chance) limit warming below 3.2°C.” Temperatures | Climate Action Tracker
They keep track of most of the pledges including all the largest emitters, and how well they are achieving, frequently updated, probably the best source on this. They conclude:
"If all governments achieved their Paris Agreement commitments the world will likely warm 3.0°C—twice the 1.5°C limit they agreed in Paris."
Their methodology is described here
As soon as we stop emissions - that's it as far as temperature increases go. But the temperature reached, whatever it is, persists for centuries. From: the IPCC here
Yes, there are some lingering minor effects such as the Siberian permafrost or removal of masking effect of anthropogenic emissions. The climate doomsdayers make a lot of those minor effects and claim they are major but there is no basis for that as we’ll see.
This is something that is often said to discredit the IPCC. But it is not true at all.
It arises from a confusion over the review process for the summary for policy makers. This is indeed scrutinized line by line by the governments worldwide as a final stage, but only to ensure that the report has been summarized accurately for the general public. They do not rewrite the report itself. This is done at the end after the report has been finished by the scientists,
There are three stages, first the experts review the entire report, then experts together with the governments, and the final stage focuses only on the Overview chapter.
The governments are involved to make sure that the overview chapter is
"is accurate, well balanced and presents the findings of the underlying report clearly."
It is most helpful for non scientists anyway and won’t make much difference to those interested in the background science who will probably focus on the main report. It does also give you an index into the rest of the report helping you to find relevant material - they give the chapter headings and sections in the overview so you can then go to the sections written by the scientists in the original report to check what it is they are summarizing.
For the scientifically literate reader anyway, it is often more helpful to start with the technical summary rather than the summary for policy makers. This is written by scientists for scientists.
The IPCC do not do any research themselves. Rather they are a review body that looks over the climate change literature of the last several years , and scrutinize it carefully, assessing things not just by the number of studies but their scientific merit and the amount of certainty in their conclusions. They are widely respected by the climate scientists.
In the 2018 report the IPCC said in their review that we can stay within 1.5 °C if we act right away. They were clear about this in both the report itself and the speeches made by the co-chairs in the extended press conference. We need to increase the pledges for the Paris agreement considerably by 2030, but we can do it. There is a mechanism in place to increase pledges every year, so this is certainly possible, if there is the political will.
The graph that came with the report shows this 1.5 °C pathway. It reaches 1.5 °C at 2040 and then levels off. Graph here.
Note that it doesn’t mean we have to stay within 1.5°C every year. Here is a more detailed version from the summary for policy makers, showing some of the possible pathways:
The observed monthly global mean surface temperature has already gone over 1.5°C. This is not the same as reaching 1.5°C in the sense of the IPCC report.
The background here is that they had many different ideas about how to calibrate their reports and predictions of possible effects of future warming.
In the end they decided on the global average surface temperature. But not on a monthly basis or even yearly, as it varies too much.
Nor the surface temperature change over a particular region - it is much more in the Arctic, and in Antarctica the world is actually cooling in a few places.
Nor the global average surface temperature over land. The average surface temperature over land varies a lot more than it does over the sea.
The Lowess smoothing there is over 5 years (locally weighted scatterplot smoothing). Latest version here
In the end they settled on the multiyear global average surface temperature. All their predictions are now calibrated to a running average of the global surface temperature over thirty years.
From: final version of summary for policy makers for the 2018 report
They chose thirty years because of multi-decadal oscillations in the Atlantic and the Pacific. These move heat from the atmosphere into the ocean where it can stay for up to several decades before it returns to the surface, warms the atmosphere and increases the global average surface temperature. On a shorter timescale we also have the La Nina / El Nino changes. The warmest years normally happen during El Nino years.
This was all hugely misrepresented in the press, even in the mainstream press.
I’ve already touched on the New York Times report which said that we need carbon pricing at $27,000 per ton by 2100, confusing mitigation costs with incentive pricing.
This is what they said:
For instance, the report says that heavy taxes or prices on carbon dioxide emissions — perhaps as high as $27,000 per ton by 2100 — would be required.
Major Climate Report Describes a Strong Risk of Crisis as Early as 2040:
This has been taken up by many other media outlets and blogs in support of climate catastrophism and the idea that it is hopeless, or that the measures are politically impossible to implement.
However this is completely mistaken. The section they got that number from says in its intro
The price of carbon assessed here is fundamentally different from the concepts of optimal carbon price in a cost–benefit analysis, or the social cost of carbon
2.5.2.1 Price of carbon emissions from Global Warming of 1.5 ºC, chapter 2, page 152
In the rest of the intro, they explain that what they are referring to here is the cost of mitigating the effects of that extra ton of CO2.
To unpack this a bit more, then, for instance, if our CO2 emissions lead to a sea level rise, that $27,000 would include a contribution to the cost of all the sea barriers to contain the rising sea through to 2100. It is a completely different idea from the pricing you need to use as an incentive to stop emitting the CO2, which is only one of many measures you might use in a combined program. Some countries use carbon pricing, others don’t.
Later in that very same section from the IPCC that the NY times misquoted, they talk about an incentive price, and they make various suggestions, mostly in the range of $5 to $50 or so depending on whether it is used on its own or as part of a larger program of measures. Taking the US electrical sector as an example they say
Furthermore, a mix of stringent energy efficiency policies (e.g., minimum performance standards, building codes) combined with a carbon tax (rising from $10 per ton in 2020 to $27 per ton in 2040) is more cost-effective than a carbon tax alone (from $20 to $53 per ton) to generate a 1.5°C pathway for the U.S. electric sector. Likewise, a policy mix encompassing a moderate carbon price ($7 per ton in 2015) combined with a ban on new coal-based power plants and dedicated policies addressing renewable electricity generation capacity and electric vehicles reduces efficiency losses compared with an optimal carbon pricing in 2030.
2.5.2.1 Price of carbon emissions from Global Warming of 1.5 ºC, chapter 2, page 153
(to make it more readable, I removed cites and rewrote USD2010 to $ and tCO2 t−¹ to “per ton”)
The NY Times journalist just cherry picked one paragraph with that high number in it, without understanding its context at all. Yet this has been taken up by so many other blogs and articles.
Search Google and this is the top result, a search snippet highlighted by Google’s algorithm:
The Hill reports it the same way as the NYTimes:
The IPCC claims in its latest report that action must be taken to avert global warming of 1.5 degrees Celsius by the end of the century — a benchmark it says comes with costly climate consequences. Its recommendation: a carbon tax of as much as $200 per ton of carbon dioxide emissions by 2030 to an astonishing $27,000 per ton by 2100.
For America families, this could mean the price of gasoline soaring to $240 per gallon. Remember when we thought $4 per gallon was high?
Gas at $240 per gallon? IPCC report lays out high cost of carbon taxes
And a Google search turns up many more articles and blog posts saying the same thing
This is all completely mistaken, as you can see from the quotes from the IPCC report itself that I just gave.
What they actually said is that if we cut CO2 emissions rapidly in the next 12 years then we can achieve a 1.5 °C rise easily. If we don't do that, it is hard to avoid 2 °C by 2050 to 2060 though we can still get back to 1.5 °C by burning lots of biofuel and capturing the CO2 from burning it for the rest of the century and other forms of carbon capture and storage. They looked at four different ways of staying within 1.5 °C.
The best is to cut emissions quickly especially since coral reefs are nearly extinct after just two years at 2 °C and delayed reductions mean a few years at 2 °C.
These are the four main pathways the cover in the report, in their investigation of ways to remain within 1.5 °C. (That’s the goal of the Paris agreement and they were tasked with both finding out what was needed to remain within this, and what the difference is between effects at 1.5 °C and 2 °C)
The first one is the one that we are aiming for at present, with no overshoot. Notice that they expect CO2 emissions to increase slightly through to 2020 with existing pledges and then with the 2020 round of pledges we need to increase our pledges strongly. It could alternatively happen in stages with some reduction in 2020 and more in 2025, and the more we delay this, the stronger the pledges have to be later on to reach carbon zero by 2050.
AFOLU: agriculture, forestry and other land us
BECCS: Bio energy carbon capture and storage (burning biofuels in power stations and then capturing the exhausts from the flues and storing it - or alternatively making it into something useful like cement
Despite what the press often say, BECCS is already proven at a commercial scale, the two components, burning biofuels and capturing CO2 from flues are both in use at commercial scale and it’s a case of combining them together. It’s not removing carbon dioxide directly from the air with technologies that barely exist.
We can do BECCS to burn biowastes which are currently generated far from where the crops grow and then just decompose and produce methane - we can burn it in power stations, and capture the CO2. A small amount of BECCS would probably be part of the solution even on the P1 path, but it’s not needed, on that path we can do it all via land use changes, soil improvement, reversing desertification and planting lots of trees through reforestation.
The P1 pathway assumes rapid reduction by 45% by 2030 and then a reduction to to 0% emissions by 2050.
C.1. In model pathways with no or limited overshoot of 1.5°C, global net anthropogenic CO2 emissions decline by about 45% from 2010 levels by 2030 (40–60% interquartile range), reaching net zero around 2050 (2045–2055 interquartile range).
It never requires a negative emissions in total, but some of the CO2 is offset by negative emissions through afforestation shown in brown in the diagram. Which is already going on, China particularly is doing a lot of afforestation.
(The yellow in these diagrams is active removal by continually recycling the trees in forests by burning biofuels and capturing the CO2)
I shared this graph before, but let’s look at it again, which shows conceptually the idea of the two approaches. The P1 path is like the one on the right, and the other ones have increasing amounts of temporary excess like the one on the left:
The other main alternative they discussed involves reaching 2 °C at around 2050-2060 but then for the rest of the century we use carbon capture and storage.
However they were widely misrepresented in the press with a claim that they required as yet unproven expensive methods for taking carbon directly from the atmosphere. This is not what they said.
Instead they said we could do it by growing vast forests for fuel and then burning that fuel in plants that capture the CO2 emissions from the fuel burning. This works because the trees as they grow take CO2 from the atmosphere and as they are burnt the CO2 is then captured and the next generation of trees repeats the process.
It would be a huge challenge to do that, but it is known technology. The main thing would be scaling up the carbon capture and storage for the emissions from the wood burning power stations. But that’s far easier than taking it out of the atmosphere with several plants already doing this.
The main disadvantages of this second approach, apart from the expense and complexity, is that it means that the corals are nearly extinct at 2 °C and it just takes a couple of years at that temperature to kill most of them to the extent that recovery is difficult.
The other two ways they discuss in the report are a mix of some early reductions and some reafforestation and biofuels with later carbon capture and storage, with more capture needed if the early reductions are less.
They didn't find any other ecosystems that are as sensitive as the corals. Not even the mangrove swamps which was one of the other ones they looked at for climate sensitivity.
The 2018 report was actually a little more optimistic than expected, if anything. They raised the CO2 emissions level needed to stay within 1.5 °C due to re-examining of past data. See
When our emissions reach a net zero (no more added than is removed) then the temperature increases stop and then start to go down as the CO2 levels reduce. However the world does continue to change and there is a lot of lag there, mainly because of the ice, and the ocean.
The permafrost would continue to melt as would the ice in Western Antarctica and Greenland. That’s a slow process because ice has huge thermal inertia.
Icebergs can spend months, and longer, in warm water before they melt. There are lakes in New Zealand that often gets icebergs from glaciers and once there they continue for ages. Bizarrely you get ice bergs in warm water in summer.
Those are icebergs in the full sunlight of a New Zealand summer day. So think how slowly ice must melt in the far colder conditions at the poles.
The poles will still experience the six month polar winter every year and only glancing sunlight even in the Arctic or Antarctic summer. So, yes, the ice in Greenland and Antarctica will melt eventually, until it reaches whatever level of cover is in equilibrium with the climate. But this is an immensely long process.
The Greenland and Antarctic ice will persist for a long time in a warmer world for much longer than the year or two of those New Zealand icebergs. Indeed both will be covered in kilometers thick layers of ice for tens of thousands of years in any of the future scenarios. It just takes that long to melt so much ice in a slightly warmer world.
The sea level continues to rise partly from this ice melting, and partly also from the sea warming up. The sea has a huge thermal capacity and will gradually take up heat from the atmosphere but that’s another thousands of years process. The warmer sea expands. For the smaller sea level rises about half the sea level rise is from the sea expanding rather than ice melting.
All that would continue, if we stopped emissions right away, but at a lesser rate than if we were going to a warmer world. About 15- 40% of the emitted carbon remains in the atmosphere for 1000 years.
However none of this changes the situation that the world slowly starts to cool as soon as emissions stop in the 1.5 °C scenario, on most scenarios that end up with zero emissions. Even as the ice melts, the world is cooling down, as CO2 gradually comes out of the atmosphere dissolved in the sea, taken up in peat bogs, swamps and salt marshes, in the soil as it builds up, and so on.
We can also remove CO2 from the atmosphere more rapidly, by burning wood and then using carbon capture on the CO2 produced - every time you do that it takes some CO2 from the atmosphere.
We can also remove CO2 by re-afforestation, and reversing desertification. Improving the soil also takes CO2 out of the atmosphere, as does making forests more species rich.
If eventually for instance we regreen the Sahara desert back to the way it was 5000 BC when it was pastureland rather than desert - that would take large amounts of CO2 from the atmosphere.
The Sahara dust fertilizes the Amazon. Massive amounts of Saharan dust fertilize the Amazon rainforest But 11000 to 5000 BC then the Sahara was green.
Green Sahara: African Humid Periods Paced by Earth's Orbital Changes
So the Amazon jungle can manage fine without the Sahara dust or less of it.
We are already doing afforestation as part of the measures to deal with climate change.
China planted nearly 79 million hectares by 2015. Under the Bonn Challenge, 56 countries, from central and south America mainly, are pledged to restore 350 million hectares of forest by 2030. All four of the IPCC's scenarios for remaining within 1.5 °C involved some measure of afforestation.
In a recent study reported in Scientific American, researchers who planted a mix of trees rather than a single species found that they removed 32 tons per hectare instead of the more usual 12 tons.
Reverting non forest land to forests globally could offset around 253 billion tons of CO2 between 2018 and 2100, which is equivalent to seven years of global CO2 emissions at current levels.
Carbon brief have a map of where reafforestation is happening around the world and with a summary of the research, and the opportunities and challenges here.
Mapped: Where ‘afforestation’ is taking place around the world
Trees and plants grow faster in a world with more CO2 due to the CO2 fertilization effect
Trees increase in productivity by around 23 percent over pre-industrial and crops boosted by 11.5 percent for most, like wheat and rice but some like corn which use a more efficient form of photosynthesis can’t benefit so much from the extra CO2 because they are so efficient at fixating CO2 already and are only boosted by 8.4 percent.
A downside is that food crops can lose a significant amount of zinc and iron in a warming world and grains also lose protein.
Ask the Experts: Does Rising CO2 Benefit Plants?
There’s a likely increase of productivity of trees by 23 to 28% until 2050. But the responses are more pronounced in young trees.
Also a study of European trees in 2018 found that though the volume increased by 29 to 100% (up to a doubling of the volume added) the density decreased by 8 to 12 percent.
So they produce much more wood, but it tends to be lighter, offsetting some of the gains.
Trees and climate change: Faster growth, lighter wood
Grasses also increase in productivity with more CO2, but it depends on the species. One study for instance found that the optimal levels of CO2 for grass depend on the species
“We found that the optimal CO2 concentrations occurred at 945, 915, and 1151 ppm for the aboveground biomass of tall fescue, perennial ryegrass, and Kentucky bluegrass, respectively.
The optimal CO2 concentrations for the growth of three perennial grass species
Overview of some of the research through to 2012 here:
The effect can also be seen from orbit with satellite measurements. Leaf area is increasing.
This greening is a combination of new leaves on existing plants as well as an increase in the amount of land covered by plants and shrubs. Only a few areas, less than 4%, show a browning effect. Many areas have an increase of more than 50%.
Rising CO2 has 'greened' world's plants and trees | Carbon Brief
The researchers estimated that 70% of the extra growth is due to rising CO2 in the atmosphere.
Another 8% is due to climate shifts in temperature and rainfall patterns, especially for high latitudes like the Tibetan Plateau and the Sahel region in Africa.
The Arctic is getting greener of course because of the melting permafrost. And the Amazon jungle areas are too however, interestingly.
Then the rest is due to effects such as more nitrogen in the soil from fertilizer, changes in forest cover, grazing and intensive farming.
This is a video summary:
It is possible that soil improvement also could make a big difference. As the soil is improved, CO2 is taken up from the atmosphere.
The amount that can be removed in this way is hard to estimate, but it could remove 200 Gt by 2100 which could increase to 500 Gt by techniques such composting (rather than burning) soil revenues, limited tilling, and mixing biochar. Currently human activities are running at just under 37 Gt in 2017. So, soil improvement could take up between 5 and 13 years of emissions at 2017 levels. I got those figures of CO2 emissions from here:
This is a summary in a recent review from 2018 of CO2 removal methods:
"In addition to mixing biochar into soils, recent studies have focused on replenishing or enhancing organic carbon in cultivated soils through various agricultural practices, such as limiting tilling, and composting (rather than burning) crop residues. … Earlier studies suggested a very limited possible role for soil enrichment; however, more recent analyses suggest a physical removal potential of ~200 Gt(CO2) by 2100, … and this could possibly be increased up to 500 Gt(CO2) by practices such as soil carbon enrichment at greater depths. …“
Evaluating climate geoengineering proposals in the context of the Paris Agreement temperature goals
This is a much shared old Scientific American article from 2013, at the early stages of the Food and Agricultural Organization’s global soil partnership. The article itself is here, as we’ll see it is hyperbole and click bait - even the Scientific American does do occasional click bait titles. It never was literally true. However it was the beginning of the FAO soil health initiative which has continued and is making a big difference to soil health worldwide.
Subtitle: “Generating three centimeters of top soil takes 1,000 years, and if current rates of degradation continue all of the world's top soil could be gone within 60 years, a senior UN official said”
It was followed up by a big report in 2015 that confirmed that preserving the health of world soils is very important and mapping out the problems and solutions. This has been followed by global action and co-ordination focused on world soil health.
This has been going on for a long time. Back in 1996, GLASOD gave this summary:
The global assessment of human-induced soil degradation (GLASOD) has shown that damage has occurred on 15 percent of the world’s total land area (13 percent light and moderate, 2 percent severe and very severe), mainly resulting from erosion, nutrient decline, salinization and physical compaction.
However, during this period, agricultural productivity has increased and food security increased. So while some of the soil is degrading, in other places we are doing things right and finding ways to increase productivity hugely through a four-fold increase in the global population.
Though soil degradation is a serious matter, there’s a lot being done to reverse desertification and improve soils.
Here is an example of what you can achieve at a local level, a rather dramatic greening the desert in the Jordan, using only the methods of permaculture. They didn’t extract water from any subsurface aquifers, just used the natural rainfall that fell on their plot in winter, and techniques of permaculture to improve the soil health:
Here is his Ted talk:
There are many initiatives underway to reverse desertification, such as the Sahara “Great Green Wall” project. It started as an idea of a literal “wall of trees” but this was not successful, and it has evolved into a vision of a mosaic of many practices, such as incorporating trees into the agriculture they are doing already and other methods of reversing desertification depending on the local situation. For instance in many places then shrubs and grass may grow better than the trees.
You can also grow food without soil. That's what aquaponics and aeroponics does. A world without soil is not a world without agriculture.
We could have a civilization on the Moon according to the dreams of space colonists, growing crops with no soil at all, or making soil directly from lunar basalt.
This is a frame from a charming Russian movie about the Moon made in 1965, before humans landed there.
Looking out on the lunar surface from inside a Moon city, in a frame from the 1965 Russian film Luna
And here is a section of the movie itself with the peaches a few seconds in:
You can also watch The full movie, in restored colour, with machine translation subtitles for part of it.
There has been a lot of research on this since then, and it does seem feasible to have agriculture on the Moon.
For more about this see my
in my Why Humans on Mars Right Now are Bad for Science. Includes: Astronaut gardener on the Moon
But we can also keep our soils in good condition.
For more on this see my
We continue to have winter and summer in all the scenarios - this does nothing to the tilt of Earth which leads to the changes of temperature between summer and winter. Where I live on the Isle of Mull, we have less than seven hours of daylight in the middle of winter, while in the middle of summer it gets so light at night that the entire night counts as twilight, never reaching complete darkness. That won’t change.
We will still have six month long winters of total darkness at the poles.
The Himalayas are also always going to be cold in all the scenarios even with no climate policies at all. Tibet, Mongolia, the high Andes, the Alps, these are all going to remain cold in all scenarios, if warmer than before.
The ice in Greenland and Antarctica is still there for thousands of years in a warming world as it takes that long to melt it all. The Arctic sea ice can melt in summer at the highest temperatures but in winter when the sun never rises at all it will still be very cold in the Arctic.
It’s a world of less ice and fewer glaciers but not no ice. So clearly not an uninhabitable world on any scenario.
James Hansen is a climate scientist, but he is well known for his hugely exaggerated statements not based on any peer reviewed research. This is an example. It was just speculation which he could publish in a book without going through peer review.
After his book was published, researchers quickly disproved it. But his book is still on sale and still quoted even though everyone in the topic of climate change knows it is wrong.
Short summary
No it can't happen. Not at present. As the sun gets hotter (which it is doing, very very slowly), yes. Maybe half a billion years from now. Maybe a billion years from now. But not in the next few hundred million years.
Incidentally over those timescales with technology there’s a lot we can do about it Simplest put shades in orbit to screen out some of the sunlight
In detail
This idea stems from a book “Storms of my Grandchildren” by James Hansen , who is a scientist but has become rather well known for his over the top climate change exaggeration. In this book, he wrote
“After the ice has gone, would the Earth proceed to the Venus syndrome, a runaway greenhouse effect that would destroy all life on the planet, perhaps permanently? While that is difficult to say based on present information, I’ve come to conclude that if we burn all reserves of oil, gas, and coal, there is a substantial chance we will initiate the runaway greenhouse. If we also burn the tar sands and tar shale, I believe the Venus syndrome is a dead certainty”
However other scientists were skeptical, for instance, as quoted by National Geographic, Raymond Pierrehumbert of the University of Chicago said
"If we were going to run away, we'd probably have done it during the PETM."
Colin Goldblatt of the University of Victoria in British Columbia followed this up by actually running the numbers, with a paper in Nature Geosciences, published in 2013. Low simulated radiation limit for runaway greenhouse climates. You can read the article in full if you click through the link from the National Geographic page Will Earth's Ocean Boil Away?
The abstract ends:
“A runaway greenhouse could in theory be triggered by increased greenhouse forcing, but anthropogenic emissions are probably insufficient”
The paper itself says it more clearly, making a similar comment to Raymond Pierrehumbert
“The so called “hothouse” climate of the Eocene is the most useful constraint for anthropogenic change. With the solar constant 1% less than today and a few thousand ppmv CO2, the mean temperature was ~ 10 K warmer than today. With CO2 and temperature both higher than we expect in the foreseeable future, this implies that anthropogenic runaway greenhouse is unlikely.”
He also makes a comparison with an earlier geological period, snowball Earth, about 650 million years ago, when possibly nearly all or most of Earth was covered in ice and snow. The concentrations of carbon dioxide built up through this period, over millions of years, as volcanoes continued to emit it into the atmosphere. This is the slow carbon cycle and normally the CO2 would dissolve back into the ocean, taken out of the atmosphere from rain or directly absorbed into the sea. But during a snowball Earth, there's no open water, or almost none, to absorb the CO2. Meanwhile the snow and ice has no effect at all on volcanoes, which continue to add it to the atmosphere as usual, and that's why the carbon dioxide builds up. Eventually enough forms to warm up the world again and the ice melts.
He remarks in the paper that when the ice melted finally, after snowball Earth, there could have been as much as 10% of CO2 in the atmosphere - compared to 0.04% right now. The sun was also 6% cooler than it is today. This didn’t lead to a runaway greenhouse either which is pretty conclusive evidence that it can't happen easily.
He mentions in the paper that if we had 10% CO2 in the future, with our 6% warmer sun, after a second snowball Earth (you would need the planet covered in ice to stop the CO2 getting absorbed in the sea to let it build up in our atmosphere to that extent), then perhaps it would trigger a runaway greenhouse when the ice melted. However, that’s hardly likely to happen for a second snowball Earth to happen with a warmer sun, so it is a very theoretical idea. Perhaps it is relevant to planets orbiting other stars?
He also talks about this in the National Geographic interview
“What my results show is that if you put about ten times as much carbon dioxide in the atmosphere as you would get from burning all the coal, oil, and gas—about 30,000 parts per million [that's 3% CO2]—then you could cause a runaway greenhouse today. So burning all the fossil fuels won't giv us a runaway greenhouse.” Will Earth's Ocean Boil Away?
His model was a simplification which didn’t take account of clouds, as he explains:
But your model does not consider the moderating effect of clouds.
That's correct. You start off with the simplest model you can, and then you build in complexity. We've calculated the maximum amount of sunlight Earth will absorb and the maximum amount of thermal radiation it will emit. So the next step will be to do some modeling with clouds in, which will probably modify the answers.
Clouds reflect sunlight, but if you put them high enough in the atmosphere, they'll also have a greenhouse effect. On Earth today, the reflection effect dominates—clouds overall have a cooling effect.
Matej Malik1 and Colin Goldblatt investigate it further in this later paper in 2016. They find that the clouds cool the Earth down by reflecting away the heat, more than they warm it up by blocking the escape of infrared into space. The end of this article has a useful summary of research in the topic up to the date of publication.
They mention another more recent paper which takes account of clouds in a detailed 3D model.
But this most recent model found that it wasn’t clouds that prevented the greenhouse effect.
This paper calculated that to have a runaway greenhouse effect, then the Earth would need to have 375 Watts per square meter from sunshine. They conclude
“With this new estimation, the inner edge of the habitable zone for Earth like planet in the Solar System is pushed inward to ∼0.95 AUs which means that the Earth should not enter a runaway greenhouse state before at least 1 billion years”.
The main thing preventing a runaway greenhouse in this model was rather, atmospheric dynamics of the water vapour.
As a parcel of moist air is heated, with no other source of water to replenish it, it becomes drier, because warmer air can hold more water vapour. As warm air rises in the tropics, it is warmed further and dried out in this way. Then the hot air is compressed as it descends in the sub tropical regions. This creates regions of drier air in the atmosphere, which, as they explain, play the role of “radiative fins” to cool down the Earth.
“As they stabilize Earth tropics today, such dynamically unsaturated regions where water vapor greenhouse effect is reduced stabilize climate against runaway greenhouse by playing the role of "radiative fins" where the emission can exceed the maximum emission for a saturated atmosphere”
What’s more, they get drier and more extensive as the sun gets warmer. The stratosphere also gets cooler (page 6).
The debate continues, as to when in the future the sun will get warm enough for a runaway greenhouse. Maybe half a billion years from now? Maybe a billion years from now? However they are generally agreed that it’s nowhere near warm enough for this to happen at present.
It needs some science fiction scenario where we import oil and gas, from Titan say (which has oceans of methane and ethane), and even then, not sure we could trigger it. We would have to be very stupid to do that. So not something to worry about.
For the background to this see my
Stephen Hawking made a similar claim. He's a brilliant physicist, everyone agrees, noted for his work in General Relativity and black holes, and he is the theorist behind "Hawking radiation" and his work is careful and meticulous in this topic area and brilliant. However he has never done any research in climate change AFAIK. The BBC interviewed him on his birthday, asking what his views are on Trump's withdrawal, and he said in the interview here.
"We are close to the tipping point where global warming becomes irreversible. Trump's action could push the Earth over the brink, to become like Venus, with a temperature of 250 degrees, and raining sulfuric acid. Climate change is one of the great dangers we face, and it's one we can prevent if we act now."
He is so famous, that whatever he says just gets reported straight, "as is". Not only by the BBC, by top papers too. Some famous people respond to fame like this, by making pronouncements in areas that are way outside their sphere of expertise, on topics that they have never studied academically. Stephen Hawking often does this.
Towards the end of his life he took to making predictions of the future, saying that we are doomed in one way or another. It’s not true. He does not present the facts, he exaggerates things and some of his predictions are frankly just bizarre. I’ve had to debunk him six times so far to help scared people.
See Debunked: Stephen Hawking’s predictions of the world ending
This was just not true. See my
Short summary
The moist greenhouse is a possible warmer world that is too hot for humans without technology. It’s not a runaway greenhouse but a stable warmer greenhouse with the oceans very hot leading to moist air that acts as a greenhouse. But it is not possible at present. The sun needs to be 3% warmer, which may happen a hundred million years from now. To put that into context it took only 66 million years to evolve to modern humans from tiny mammals the size of shrews scurrying at the feet of dinosaurs.
In detail
Popp et al, in a paper published on 2015, found another stable state that an Earth like warm water world could flip into, if the sun was 3% warmer than it is today. (Total Solar Irradiance 1.03 that of today). In the second half of the paper they show that it could also get into this state with 770 ppm of CO2 in the place of a brighter sun. See Transition to a Moist Greenhouse with CO2 and solar forcing.
This is a 3D model of a pure aqua planet with no land. They find a new steady state with a global average sea surface temperature of 330 °K or about 57 °C. Though not a Venus type greenhouse, it would be too hot for humans to survive, without technology - and with so much water in the atmosphere, right up to the upper atmosphere where the Sun can dissociate it into hydrogen and oxygen, it would rapidly lose all its water to space.
You can't transfer this directly into our Earth's case, because of the mix of land and sea. In the second half they discuss what levels of CO2 could flip an Earth like planet with our mix of land and sea into a state like this, coming up with a figure of several thousand ppm.
It's a possible future for Earth hundreds of millions of years into the future, or for exoplanets. It doesn't seem that we could tip Earth into this state quite yet, even if we burnt all our coal, oil, gas etc. But it's rather closer to our present state than the Venus hot greenhouse.
That is still practically forever for humans. A future "moist greenhouse" with most of Earth too hot for humans to live in. However on such vast timescales we are not likely to remain human in form, surely evolved to some other hominid, unless we use artificial means to prevent further evolution such as genetic modification back to humans of our time. There may well also be other intelligent creatures in our civilization - maybe by then octopuses, giant squids, elephants, parrots, dogs, may all have evolved into intelligent species and be co-existing with us.
So it would be a question of whether the climate is right for their and our future descendants after another 100 million years of evolution.
It would be well within their capability to move Earth or to shade it from the sun, if they continue with technology for 100 million years. Or to build numerous habitats in space. I don't think we need to concern ourselves with their prospects at present, except to leave Earth in as good condition as we can.
For the background to this see my
I’d like to do a bit of an aside here to help people who are panicking about this. I often get people contact me scared of things that couldn’t possibly do anything to them. This may be obvious once I say it but it needs to be said for some people who are really scared and not thinking clearly, also for very young children.
You will get natural hazards like the fires, heat waves, flooding and hurricanes. And we’ll get more of those as a result of climate change. But don’t think of them as covering the entire world. That just can’t happen.
For instance, you are not going to get a heat wave at all if you live somewhere really cold like lose to the Arctic circle.
You aren’t going to get a proper hurricane if you live in Europe, because hurricanes cross the Atlantic from West to East and never make landfall in Europe (strong winds yes, hurricanes proper, no).
You aren’t at risk of a forest fire if you live in a place without trees.
The sea in worst case rises meters by 2100. The IPCC talks about it being feet, but it is possible it could be higher than their estimate because they caution that the science is not yet well settled on this. But not tens of meters for sure. And not the kilometers rise needed to swamp the entire world - there isn’t enough ice to melt to do that ever.
For instance this is what happens to Florida with a three meters sea level rise. This is much higher than the IPCC projection for 2100 of two to four feet, and although that is regarded as conservative, it’s not likely it’s as much as three meters.
Florida before and after a 3 meter sea level rise due to melting ice from the Antarctic and Greenland ice sheets. Image made using the Eustatic Sea Level Change tool from Virtual Earth System Laboratory (VESL).
Florida is a low lying state, yet most of Florida also is untouched at a three meters rise.
If you live in the Florida keys or Miami, yes you may have to move house. Florida is especially vulnerable because the land is porous limestone. For New York, or Netherlands they can build higher flood barriers. For these low lying areas in Florida the worst case is you move out or build upwards (e.g. artificial islands) or get used to Miami having flooded streets at extreme high tides.
So, yes that can happen. But I get people worried about sea level rise who live nowhere near the sea. It doesn’t mean that the entire surface of the Earth is covered in water to a depth of one meter. You are only at risk if you are in a city that is already close to being flooded.
Also for people who do live close to sea level, just a meter or so above the high tide mark - it is only a risk of flooding at the highest tides with storm surges to start with. Even with a one meter rise or more, you are not going to be flooded at low tide or indeed, any time except the highest spring tides once a lunar month with assistance of storms.
The worst case is you have to evacuate Miami or convert it into a city that is a bit like Venice during the occasional high tide storm surges with sea filling the streets.
Everyone else, then it’s just like normal flood warnings, wildfire warnings, heat wave warnings and hurricane warnings, but maybe more of those in the future.
The wildfires are only a risk if you are in a place like California already at risk of fires. It’s not talking about fires, and flooding sweeping over the entire world, or of a global hurricane that affects everyone worldwide - no such thing is even possible.
Let’s look at the “RCP”s or Recognized Concentration Pathways. These are detailed scenarios worked out so that climate modelers can run their models on the same projections for comparing them. If it weren’t for them, everyone would use different scenarios and it would be almost impossible to either compare models or aggregate them together for statistical results.
For details:
This shows how the CO2 levels vary with the different RCP’s and the emissions which are the inputs to the models:
They are all pretty much indistinguishable up to 2020.
I got these graphs here:
If you look at the latest data - we are on the same curve as RCP 6.0. But it’s also on RCP 4.5 and 2.6 - the 2 °C and 1.5 °C pathways. We just can’t tell them apart yet from the graphs but by analysing policies we are on the path for a 3 °C rise by 2100 :
From Analysis: Why the IPCC 1.5C report expanded the carbon budget | Carbon Brief
This shows how the atmospheric CO2 and the temperature and sea level rises over a longer time period through to 2500 with the four scenarios. In the RCP 8.5 then there just aren’t enough fossil fuel reserves to keep burning them for ever which is why that curve is shown as leveling off at 2000 ppm in 2200 for “business as usual”.
Figure 2.8 - IPCC from the AR5 Synthesis Report in 2013
Notice how when the atmospheric CO2 levels stop rising, the temperatures almost immediately level off in all the scenarios. However the sea levels continue to rise in all the scenarios except low CO2, for centuries.
Those sea level rises are difficult to model and could be up to several times larger.
So anyway that's what the IPCC say in their summary of the research on the topic for the last few years. 1.5 °C is definitely in reach if we have the political will. It requires ramping up pledges rapidly in the next several years through to 2030. But the aim is to ramp up.
If we stop CO2 emissions, then whatever temperature it is is where we level out. If we could stop all CO2 emission today then we would level of at 1 °C above pre-industrial and then it would gradually decline.
We are not going to be able to stop instantly, that isn’t going to happen. But it shows that the rise is not inevitable until we actually reach those temperatures. That is the conclusion of the IPCC.
So now, let’s look at those delayed effects, that the doomsday sayers / climate catastrophists make so much of.
Many of those posts that say we have a much higher temperature rise baked in rely on the clathrate gun hypothesis, which is effectively disproved now.
This is how it is supposed to work:
The clathrates are a form of ice with methane locked inside it, on the floors of the Arctic ocean. It floats in water like ordinary ice, so any that remains on the sea floor has to be bound to the sediment. It’s stable at higher temperatures than ordinary ice, up to a few degrees depending on pressure. There are thick deposits frozen into the sea bed below the Arctic ocean. The only ones that matter are the ones within 100 meters of the surface. Any deeper and the methane dissolves out of the bubbles into sea water on the way up to the surface as the sea is very undersaturated in methane.
However it’s now known that only the top layers of the clathrates are warm enough to start to destabilize only the top 1.6 meters and they do so only very slowly (centuries) because they are only warmed sufficiently for less than half the year - and this doesn’t seem to be enough for fast destabilizing.
There have been skeptics all along- it is thermodynamically difficult because it's an endothermic reaction - the opposite of the idea of an explosion you get from the word "gun". If you try to get it going, some will dissociate, absorb the heat and that will cool down the rest and it just stops. Carolyn Ruppel, lead author of the USGS metastudy puts it like this:
So the deposits locally can't explosively dissociate. It would need a huge feedback into the global climate to do this, but the metastudies show that this just isn't present. Instead it is a very slow burner over thousands of years, not even much affected by the increasing temperatures, since they have been warm enough to destabilize already for thousands of years.
The USGS metastudy in 2017 by the USGS Gas Hydrates Project concluded
"“Our review is the culmination of nearly a decade of original research by the USGS, my coauthor Professor John Kessler at the University of Rochester, and many other groups in the community,” said USGS geophysicist Carolyn Ruppel, who is the paper’s lead author and oversees the USGS Gas Hydrates Project. “After so many years spent determining where gas hydrates are breaking down and measuring methane flux at the sea-air interface, we suggest that conclusive evidence for release of hydrate-related methane to the atmosphere is lacking.”
Gas Hydrate Breakdown Unlikely to Cause Massive Greenhouse Gas Release,
That’s from the big USGS review in 2017, and the Royal Society did one too and then in 2018 the big gas hydrates research project CAGE finally proved that the methane has been leaking gradually for millions of years and is not a new thing . It is pretty much settled. It’s not even a consideration at all for climate modeling now.
For more about this see this, my update of the Wikipedia article which is now very dated on this topic and sadly they don’t seem likely to update it any time soon, so I’ve done my own update of it in our Doomsday Debunked wiki to include the latest research from 2017 though to 2018:
More recently those who say that the IPCC have left out big unknown effects have switched to the Siberian permafrost. This is nothing to do with the clathrate gun hypothesis. Indeed, it is not about methane clathrates at all - there is some methane locked into the permafrost already, but not a lot.
Instead it’s just ordinary ground filled with frozen grass, other vegetation, bodies of animals (including mammoths in Siberia) and other creatures that have been frozen for thousands of years. Also a lot of it is just frozen peat. As the climate warms up then gradually the permafrost melts. It's a slow process. As that happens those organics are exposed to liquid water and the atmosphere. Parts that are dry produce CO2, but can also take up CO2 from the new vegetation that grows on them. Also as the permafrost melts, peat will start to grow over large areas and peat growth takes up a lot of CO2.
Parts that are wet, not well drained, can produce methane because in wet conditions somewhat blocked off from the surface, without access to air, then decomposing microbes tend to produce methane instead of CO2. They do that just because there isn't any oxygen available to make the CO2. So it attracts different kinds of microbes that produce methane instead.
Because the methane is produced below the surface, most of it gets converted to other organics and to CO2 as it gradually percolates towards the surface.
Figure taken from this paper showing some of the processes. The methane is produced deep underground. It gets involved in many chemical reactions. Methane is produced in anaerobic conditions conditions without much oxygen - and it is consumed in aerobic conditions.
This makes it really hard to estimate what would happen as it melts, because there are so many different processes going on. The research is conflicting but while laboratory experiments tend to suggest that it will release a lot of carbon, a fair bit of the actual field research, looking what happens when it melts, suggests it could be carbon negative at a 3 °C rise. The modeling also suggests that this is well within possible.
If the melting is fast, then it could be an extra eighth of a degree rise by 2100, and a slow burner through to the next three or four centuries. That is for “business as usual”. This is based on paper from 2011 for the eighth of a degree (190 tons by 2200, see paper)
For slower melting, a 2.4 °C rise by 2100 and then level out, then it’s much lower, perhaps a twelfth of a degree by 2199 with most of that after 2100. This is based on a major metastudy review in 2018 of many papers on the topic concluded that if we remain within the 2.4 C pathway, it is possible that it remains carbon negative and removes 66 gigatons by 2299, and at most it adds 70 gigatons by 2299 (paper).
Most of us aren’t used to thinking in terms of gigatons of CO2, so to get a rough idea of what that means, I used the expanded carbon budget from 2018, which gives a figure of around 420 gigatons for a 0.5 C rise, to give a rough idea of how this converts to a temperature rise. Of course it would depend on modeling to get it exact.
Also we may be able to influence what happens by drainage or irrigation. For instance damp ground may encourage peat formation which takes up CO2.
If we were to discard all our climate policies and return to "business as usual" then this time all the models do show a positive CO2 contribution but even then it is not huge. It can be anywhere between negligible and about a quarter of a degree of contribution by 2100.
This is potentially a significant amount, but it's only going to introduce an error of at most a quarter of a degree, and on the path we are on, the effects before 2100 are likely to be negligible, and possibly carbon negative.
I cover the details here.
There are several other things like that including the Arctic albedo. This is about the way that when ice melts, the ocean becomes less reflective, because it’s not covered in that white stuff, and so absorbs more heat. The climate doomsdayers make a lot of that but it is already included in the IPCC models. It is a minor effect globally.
The ice only melts in the Arctic summer - rather obviously when the sun is below the horizon throughout the arctic winter any albedo effect is non existent because of the permanent night. That will be true no matter what happens.
The albedo effect is only really relevant to the melting of Arctic ice in summer - it makes the water slightly warmer so increasing the amount of ice melting. It is important to polar bears and walruses mainly. But even in summer the sun is low on the horizon in the Arctic and not that much heat is absorbed by the ocean. It matters locally but globally it’s not a significant effect.
The Arctic will probably become ice free in summer occasionally, some time mid century but it is not likely to become ice free in winter at all, not on any projections I've seen. The IPCC do take account of albedo effects of ice and snow.
Another such effect is the effect of the Amazon forest die back but that is now thought to be much less than previously estimated. They didn't take account of the effect of the mix of species some of which are more resistant to heat changes than others. See this paper in Nature from 2016
Then another factor is that some patches of the forest are more resilient than others.If it was a monoculture the climate would just need to go over some threshold in temperature, or humidity, and the whole thing would go. Because of the mix of species then it is more of a gradual thing. And then because of the patchiness, it would change to grassland only in patches which protects it further. Also parts of it seem to be much more resilient, especially the western part of the Amazon rainforest, and this is how it survived previous warm periods, so it’s now thought most of it would survive this time too. See this paper in Nature for some of the recent research from 2018:
So in short, the composition of parts of it would change. Some might change to a more open drier grassland. However most of it would remain and there would be a lot of tropical rainforest still at 3 °C or even at the higher temperatures of “business as usual”.
The IPCC review doesn't take account of papers on these topics for detailed projections but it does take account of them in separate sections looking at how much they might affect the conclusions. And the result in the reviews is that they have some effect but it is minor enough that it doesn't matter that they leave them out. So they have a reason for leaving them out.
This is often not mentioned by those who criticize them for this.
What they do is a careful systematic review. That's their job. And that also is why it takes so long, it's easy to do a hasty non systematic review like those of their critics, but not so easy to do a careful systematic review.
The IPCC don’t actually do any research themselves. The people who do the review are experts who do their own independent research of course, but that’s not their role in the IPCC, it is to do a systematic thorough review of the researches by others over the last several years.
This is why I rely on the IPCC over the people who do their own independent analysis. I’m no expert myself and they are people who have spent years of their life studying the material to make the most accurate assessment they can. And when there are differences of results and views in the literature, they do not just pick one favoured one. Rather, they summarize the range of results or say things such as “high confidence” if there is general agreement or “low confidence” if there are diverging views or if the research has gaps in it.
And yes, scientists who do the climate change projections acknowledge that there are some things they leave out of their projections. This is true. What the critics often don’t mention is that they give reasoning about why they think it is okay to leave them out.
Journalists sometimes refer to “feedback” when they really just mean amplification. A 3 °C warmer world may have a fifth of a degree extra temperature rise from Siberian permafrost by 2200. But that is not a runaway effect - that extra warmth is not enough to significantly increase the melting of the permafrost. If we stop human emissions of CO2, it will just warm by an extra fraction of a degree and then stop.
In this quote then “threshold behaviour” refers to the idea that once you reach a particular temperature some runaway effect will arise that commits you to a much higher temperature. In a systematic review, no such effects are known.
See Royal Society review of research from 2017
Permafrost: …. This led to a new estimate that about 100 Pg of cumulative carbon emissions (with a wide uncertainty) would be released from thawing permafrost by 2100 under RCP8.5. This leads to a significant positive feedback, but the review emphasized that emissions are “likely to be gradual and sustained rather than abrupt and massive”. A recent modeling study estimated that permafrost carbon releases could contribute up to 12% of the change in global mean temperature by 2100 Studies since 2013 therefore confirm the importance of permafrost carbon release as a positive feedback, and the need to include it accurately in Earth system models, but they do not support considering it to exhibit threshold behaviour.
Clathrates: Some economic assessments continue to emphasise the potential damage from very strong and rapid methane hydrate release, although AR5 did not consider this likely. Recent measurements of methane fluxes from the Siberian Shelf Seas are much lower than those inferred previously. A range of other studies have suggested a much smaller influence of clathrate release on the Arctic atmosphere than had been suggested. …. A recent modeling study joined earlier papers in assigning a relatively limited role to dissociation of methane hydrates as a climate feedback. Methane concentrations are rising globally, raising interesting questions (see section on methane) about what the cause is, finally new measurements of the 14C content of methane across the warming out of the last glacial period show that the release of old carbon reservoirs (including methane hydrates) played only a small role in the methane concentration increase that occurred then.
Amazon rainforest: The processes acting on tropical rainforests are very complex and a recent review still emphasised the possibility of a climate threshold … Recent work using a detailed ecosystem model (Levine et al., 2016) supports the possibility of a significant but heterogeneous transition in biomass type dependent on the length of the dry season, but in a continuous rather than “tipping point” manner. Resilience may be underestimated if plant trait diversity is not included in models
Since then one other such effect has come up, the cloudless skies study - it's about a particular type of cloud that forms low over the sea and clears away rapidly at very high sea temperatures warming the planet up in one discrete step by up to ten degrees C in a few months or years. However, if you look at it closely they don't expect it to happen until well into the next century even with "Business as usual" which we are not on (see below).
The oceans are getting more acidic. But they are still alkaline rather than acid and will remain more alkaline than acidic in the future too. So in a way it is a bit of a misnomer. Not actually going to get a pH lower than 7, but less alkaline than they are now.
At times our oceans in the past have been more acidic and they have had sponge reefs, and corals go extinct. At other times they are more alkaline and have corals as today, and sponge reefs are rare.
Some species will benefit from acidification, for instance sea grasses. The NNOAA put it like this:
Ocean acidification is expected to impact ocean species to varying degrees. Photosynthetic algae and seagrasses may benefit from higher CO2 conditions in the ocean, as they require CO2 to live just like plants on land. On the other hand, studies have shown that lower environmental calcium carbonate saturation states can have a dramatic effect on some calcifying species, including oysters, clams, sea urchins, shallow water corals, deep sea corals, and calcareous plankton. Today, more than a billion people worldwide rely on food from the ocean as their primary source of protein. Thus, both jobs and food security in the U.S. and around the world depend on the fish and shellfish in our oceans. What is Ocean Acidification?
The polar oceans are predicted to be the first to become acidic enough to make a significant difference, to become undersaturated with respect to carbonate. Moluscs are resilient to the ocean acidification. But some tiny creatures are more vulnerable. So also are corals. That’s because they use aragonite, an especially soluble form of carbonate.
Corals generally need the aragonite saturation index to be at least 3. They can manage at lower values but are particularly vulnerable to coral bleaching because at lower values then the bleached coral starts to dissolve away. So as the oceans get more acidic, then corals will be more vulnerable to bleaching events.
That’s partly why they are so sensitive to temperature changes.
Some coral reefs already live in conditions of much lower pH of 7.8 instead of 8.1 due to volcanic carbon dioxide seeps in Papua New Guinea. This corresponds to an increase to 750 ppm by 2100, a likely level to reach with current policies).
They were able to survive with constant coral cover but different species mix and less structural coral though the same amount of cover. But at pH 7.7 the reef building ceased.
It’s a combination of the warming and the acidification. Corals can respond by moving to colder places but not if the change is too fast. See the section on ocean acidification in this review for more details:
It may be possible to help save some of the coral reefs from the worst impacts by actually growing coral larvae in the lab and then reintroducing them to coral reefs to revive them.
Amongst the most vulnerable species are the sea butterflies or pterapods. Tiny planktonic creatures.
They use aragonite, an especially easily dissolved form of calcium carbonate. Their shells are already dissolving in our slightly more acidic oceans in some parts of the world, as was shown in this study in 2012.
However as an example of how this is work in progress, recent research published in 2019 shows that they are able to cope with this even when the outer shell dissolves away completely, by thickening the internal shell wall. Though it likely has some metabolic cost, the pteropods are surviving as the oceans become more acidic.
Pteropods counter mechanical damage and dissolution through extensive shell repair
They conclude their paper
We do not claim that L. helicina will be immune to ocean acidification on account of their ability to maintain their shells, but propose efforts should shift to assessing the metabolic cost of repair calcification when predicting the tolerance of this species to future environmental conditions.
There is no doubt that ocean acidification will lead to major changes with some species being badly effected and some benefiting from it. The details are complex with much research still to be done.
It’s a significant issue but we are not talking about uninhabitable oceans or all the ocean creatures dying or anything like that.
The Wikipedia article is a useful source for cites on this
This is the idea that aerosols from burning coal and other human activities can have a cooling effect and may be masking some “baked in global warming” due to a dimming effect.
However it is more complex than just a masking effect. The SO2 has a cooling effect while soot and other black organic compounds have a warming effect. The aerosols also don’t decrease to zero when you stop burning coal, but rather, a gradual reduction.
They do partly offset the mitigation efforts in the early stages. In the latest IPCC report they say that the deep reductions that stay within 1.5 °C with no or limited overshoot have to include deep reductions in methane and black carbon, 35% or more of both by 2050 relative to 2010. When you do that then the cooling aerosols are indeed also reduced and this partially offsets the mitigation measures for two or three decades
If we were to stop all emissions instantly, it's a 0.15 °C bump lasting for 20 years.
Global Warming of 1.5 ºC - chapter 1, figure 1.5
If we stop all aerosol emissions, yellow line, there is a short term bump in temperature by 0.15 degrees, and returning to the previous temperatures in 20 years and ending with a reduction to 0.25 °C below the present by 2100
This shows the sharp reductions in methane and soot needed for the 1.5 °C path:
This is both good for health and also has a cooling effect which is indeed offset to start with by the warming effect of removing the masking sulfur dioxide aerosols.
I’ll include quotes to help those who want to follow this up further to see which part I’m referring to:
“C.1.2. Modelled pathways that limit global warming to 1.5°C with no or limited overshoot involve deep reductions in emissions of methane and black carbon (35% or more of both by 2050 relative to 2010). These pathways also reduce most of the cooling aerosols, which partially offsets mitigation effects for two to three decades. Non-CO2 emissions can be reduced as a result of broad mitigation measures in the energy sector. In addition, targeted non-CO2 mitigation measures can reduce nitrous oxide and methane from agriculture, methane from the waste sector, some sources of black carbon, and hydrofluorocarbons. High bioenergy demand can increase emissions of nitrous oxide in some 1.5°C pathways, highlighting the importance of appropriate management approaches. Improved air quality resulting from projected reductions in many non-CO2 emissions provide direct and immediate population health benefits in all 1.5°C model pathways”
There may be a “baked in” warming, but if so, it is likely to be less than half a degree.
You can download the chapters from this page: Download Chapters
From chapter 1 Executive summary
Past emissions alone are unlikely to raise global-mean temperature to 1.5°C above pre-industrial levels (medium confidence), but past emissions do commit to other changes, such as further sea level rise (high confidence). If all anthropogenic emissions (including aerosol-related) were reduced to zero immediately, any further warming beyond the 1°C already experienced would likely be less than 0.5°C over the next two to three decades (high confidence), and likely less than 0.5°C on a century time scale (medium confidence), due to the opposing effects of different climate processes and drivers. A warming greater than 1.5°C is therefore not geophysically unavoidable: whether it will occur depends on future rates of emission reductions. (page 51)
This is very hard to study, there may even be no effect. From Chapter 2.2.1.1 Geophysical uncertainties: non-CO2 forcing agents
The total aerosol effective radiative forcing change in stringent mitigation pathways is expected to be dominated by the effects from the phase-out of SO2, although the magnitude of this aerosol-warming depends on how much of the present-day aerosol cooling is attributable to SO2, particularly the cooling associated with aerosol–cloud interaction (page 101)
How much CO2 is taken up naturally by the ocean, land etc?
We do have a fair bit of help here from nature. The oceans and land are constantly absorbing CO2 from the atmosphere, in addition to the seasonal cycles. Only 40% or so of the anthropogenic emissions remain in the atmosphere, and this will continue once we stop emissions. From the: Global Carbon Budget 2018 (Journal Article), this is a summary of their findings, showing the historical change of the yearly emissions and absorptions
For the last decade, 2008 - 2017, then they work out
Total around 10.9 gigatons per year
(note, the numbers may not add up to 100% due to rounding errors)
This is another recent article, March 2019. It says 31% of anthropogenic emissions emitted between 1994 and 2007 have been absorbed in the oceans. Whether it continues to do this depends on the CO2 concentration in the atmosphere and whether the surface layers of the sea are saturated (as most of the CO2 doesn’t get any deeper than 1000 meters from the surface.
It also depends on the ocean temperature, currents and other details of multi-decadal oscillations in the oceans. They found for instance that the CO2 absorption in the Northern Atlantic has decreased recently but increased in the Southern Atlantic.
This percentage of CO2 taken up by the oceans has remained relatively stable compared to the preceding 200 years, but the absolute quantity has increased substantially. This is because as long as the atmospheric concentration of CO2 rises, the oceanic sink strengthens more or less proportionally: the more CO2 is in the atmosphere, the more is absorbed by the oceans – until it becomes eventually saturated.
So far, that point has not been reached. “Over the examined period, the global ocean continued to take up anthropogenic CO2 at a rate that is congruent with the increase of atmospheric CO2 ,” Gruber explains."
The Arctic is the most vulnerable to heating. But the UN report that said 5 °C is already locked in was a mistake, a typo, it should have said 0.5 °C.
If we keep to the Paris target of 2 °C then the warming is 0.5 to 5 °C in the Arctic region by the 2080s above the temperatures relative to 1986 to 2005 as the baseline
Climate-model runs for the region between 60N and 90N for the winter months (December, January and February) for the 32 different climate model (one run per model).
The models followed RCP 2.6, corresponding to a 2 °C target,
Factcheck: Is 3-5C of Arctic warming now ‘locked in’? | Carbon Brief
And this shows what happens to Arctic warming with all the scenarios
The idea of RCP 8.5 is that we keep up current emissions through to the end of the century. To do that we would need to reverse all the recent pledges and policies. But even that would not be enough.
In many places renewables are already competing with fossil fuels, for instance in Australia and in the US, and we have major initiatives in many countries to switch to renewables. And that’s with existing technology. Prices are rapidly falling, and there is no sign it will stop.
That’s a ten-fold reduction in price from the mid 1990s to the mid 2010s - from this 2018 paper Evaluating the causes of cost reduction in photovoltaic modules
The main reasons for the reduction in cost from 1980 to 2012 are increases in efficiency, reduction in material costs, and reduction in the amount of silicon used. In the recent decade, increase in plant size has been a major factor, with China particularly having huge plants that reduce the costs enormously through economies of scale.
At a high level, government R&D contributes most to the reductions, though since 2001, then economies of scale have taken over
The paper recommends more government R& D saying
Economies of scale in particular have had a greater impact more recently, and likely offer an avenue for further cost reductions. Notably, the typical 2012 plant size in our data set has been surpassed by several new Chinese plants with typical sizes of 1–2 GW/year. However there may be a limit to how much plant sizes will grow, and savings from economies of scale may be exhausted over time.
R&D, both public and private, was a key driver of module cost reduction historically and can be valuable going forward in improving module efficiency and reducing materials use. Improvements to module efficiency in particular would help cut the per-watt cost of all cost components of PV modules (as well as PV systems).
Discussion of it in Ars Technica How the falling cost of solar panels can teach us to make new tech affordable
Discussing this paper, one solar panel company in the US, Wood Mackenzie, Ben Gallagher, a senior solar analyst with Wood Mackenzie Power & Renewables forecasts that the prices will continue to fall rapidly in the future:
Wood Mackenzie forecasts that spot prices for modules could fall from $0.30 per watt-DC to $0.18 per watt-DC in the next five years, a 40 percent drop. And R&D is only part of the equation.
According to Wood Mackenzie, the main factors contributing to this decrease will be the growing automation of factories and the use of diamond wire saws to cut material loss in the silicon wafer manufacturing process.”
Finally, cell manufacturing equipment is becoming increasingly efficient, reducing power consumption. “All of the material inputs to making a solar panel are still falling,” Gallagher said.
It would need strong incentives for fossil fuels to keep us using them rather than renewables worldwide. Not just one president for one term. Not just one country either. All the main countries determinedly burning fossil fuel and discouraging renewables as they continued to get lower cost and more efficient, for 80 years!
Even a 12 °C rise is not remotely apocalyptic. Earth right now is warmer than it was during the ice ages but on a larger timescale it’s the coldest it has been for 450 million years.
Usually there is no ice at either pole The water at the poles can reach temperatures of up to 10 °C. Even the worst of the climate change predictions come nowhere close to that. We will have ice in Antarctica for centuries, probably thousands of years into the future.
At times in the geologically recent past the world has been so hot that there were palm trees as far north as the Arctic circle, no ice at either pole and typical polar temperatures 10 °C.
500 million years of climate change. As you can see, on the timescale of millions of years. Earth has never been this cold for the last 450 million years. In this diagram, one part per thousand of oxygen 18 corresponds to around 1.5 - 2 °C
Most of the time Earth has no ice at all at its poles, no permanent ice at all except at the top of high mountains. Compared to that, the Earth is unusually cold at present. We are in the middle of an interglacial but geologists would say we are in the middle of an ice age still, technically, since we have permanent ice at the poles.
The worst case with “business as usual” which we are not headed for is mass migration of humans from the hotter parts of the world such as the Persian gulf and the hottest regions of India, not mass extinction. Parts of Northern India of course are very cold near the foothills of the Himalayas and they will not get too hot for humans even on the very worst scenarios. We aren’t headed for a future where Nepal, Bhutan or Tibet will be too hot for humans on any scenario. Or Ladakh or Gangtok in India.
This is a map from a paper that studied the northern Chinese plain, where many farmers grow rice and work out of doors. It’s especially vulnerable because of the humidity. Even then the climate is fine for the rice. The problem is the effect on humans working in the fields.
The graph is here Nature Communications
The red means business as usual RCP 8.5, the blue is RCP 4.5 approximately what we are on so far with the Paris pledges and unconditional commitments, and the black is historical. The graphs are histograms showing the predicted number of days with at least 6 hours of maximum wet bulb temperatures for each bin in the thirty years time period from 2070 to 2100 in each scenario.
Over 35 °C then even the fittest farmers would not survive six hours of working in the fields. Work would have to stop.
They focused particularly on China but looked at two other study regions, India and the Persian gulf.
The dark red areas have wet bulb temperatures over 31 °C for 5% of the time, and risk 35 °C heat waves. You can see how it affects eastern China (above Taiwan in the map) also the coasts of the Persian gulf (but not the desert interior because it is so dry there) and Bangladesh, Kolkata and parts of Pakistan.
The figure is here Nature Communications
(with link back to the article page).
For other parts of the world we can go to another study here
This time it shows the yearly probability of a heat wave that has temperatures over 55 °C. Whether that has a high wet bulb temperature would depend on the humidity, and you can get conditions too hot in very damp conditions below that temperature. So it’s not as precise but you can see that other areas that need attention would include southern US and northern Australia, and central regions of southern America. Orange means temperatures over 55 °C are experienced roughly every other year.
Paper here
So it does become an issue for some people already at 4 °C.
The Persian gulf region is particularly vulnerable because of shallow seas, and intense sun, leading to hot damp conditions - the most difficult conditions for humans to survive in. Elahir and Pal, reporting in Nature, found that at "Business as Usual", many major cites could reach a tipping point later this century, where for the first time, conditions exceed the limits for human survival, with wet bulb temperatures exceeding 35 °C every few decades.
This is for a higher temperature rise usually estimated at about 4.9°C global warming from pre-industrial.
(click to watch on Youtube)
See.MIT press release:
Christoph Schaer wrote in commentary on this study (which he was not involved in) that while deadly heat waves have occurred recently in Chicago, Russia, and Europe, in these cases infants and the elderly were most affected. This he says
“Concerns another category of heat waves — one that may be fatal to everybody affected, even to young and fit individuals under shaded and well-ventilated outdoor conditions.”
So, such conditions as they describe can occur, but not at 3°C anywhere.
They can occur, towards the end of the century, but only at "Business as usual". We are not headed there. The IPCC worst case is 3°C by 2100, because it is not plausible that we continue to burn fossil fuels through all the transitions to a 4.9°C warmer world without doing anything to mitigate it. Even if improbably the Paris agreement fell apart (it is well established now since the rule book was agreed in December 2018), there is no way that we continue to ignore the crisis through to the second half of this century. Even in that worst case they predicted action, but disorganized and late, enough to keep us within 3°C.
As it is, we are headed for 3°C already with existing pledges and with a great deal of leeway to let us ramp up to higher pledges which we can definitely do in the next decade consistent with prosperity and increasing quality of life worldwide.
See my
in the worst case, which we are not headed for, the UK becomes like Spain. Well, people have been living in Spain for thousands of years. We aren’t going to die because we have Spanish temperatures here.
We are not headed for this scenario, nothing like it, with existing policies only a 3 °C rise. But if it gets 10 °C warmer, Aberdeen (14 °C) becomes like Barcelona (24 °C) and Barcelona like Dehli (34 °C) . The worst outcome is that we end up growing oranges and bananas in the UK, not that the UK becomes too hot for humans or that we can’t grow crops at all here anymore.
We will need to adapt, sure. Right now people in England die during a 30 °C heat wave that would be just normal in a Spanish summer. We don’t even have air conditioning in most UK houses. We need to get used to needing it, if the world gets as warm as that.
But for most of us, then other people already know how to live in those conditions and we can learn from them.
Some people in the very hottest parts of China, India, Persian gulf, United States and others, especially in hot wet places will find it gets too hot to survive at all without air conditioning. But this only happens at a global rise above 4 °C.
It’s not the heat that gets you, but combination of moist air and heat. You can keep cool by sweating, but above around 35 °C if the air has 100% humidity almost nobody can survive. You’ll die within a few hours if you can’t get somewhere drier or colder. Above 37 °C with 100% humidity, then that is above blood temperature and your body no longer can cool itself even slightly and you soon are dead.
But you can survive by either cooling the air down or drying it out. Even in a world like that, people with enough confidence in technology could ride out the hottest heat waves in India, China etc, and of course many plants would be fine, you could still grow rice, maybe largely automated cultivation, and crops that like really hot conditions.
It would certainly have lots of climate migrants. But even in India or China, to different parts of the same country. The north of India, the foothills of the Himalayas are pleasantly cool and eventually really cold. Same for China, and nearly all of Tibet, Mongolia etc.
Meanwhile Canada, Russia, especially Alaska and Siberia would become warm “des res” places for humans. They would begin to be places where you can use conventional agriculture in fields.
If it gets 10 °C warmer, Aberdeen (14 °C) becomes like Barcelona (24 °C) and Barcelona like Delhi (34 °C) .
The worst outcome is that we end up growing oranges and bananas out of doors in the UK, mangoes, sugar cane and avocados in France, and perhaps coconuts in the Mediterranean
Might this be a familiar Mediterranean sight in a warming world?
The Lone Coconut Tree , Kannur, Kerala, India. Prof. Mohamed Shareef from Mysore
Blog post here about someone who managed to grow a coconut palm tree in Southern Italy
Farmers may have to grow new crops. There’s also though research into making the crops they already use more heat tolerant. This is research into finding heat tolerant beans that can grow with night time temperatures as high as 23 °C about 4 °C higher.
This is a project for US cities only, sadly. But it finds climate analogues in a warming world. For instance if you live in Washington DC, their map can help you find a city with climate similar to what you will experience in 2080.
To work out the analogue they used the minimum and maximum temperatures and the total amount of precipitation (rain, snow etc) for the four seasons of the year. So a close analogue means the temperature range and the amount of precipitation is the same for all four seasons. A weaker analogue means that they are only roughly the same.
The online interactive version of it just shows the closest analogue, for high emissions is 4.9°C by 2100, and doesn’t tell you how close or far it is as an analogue, but it gives a rough idea:
For reduced emissions, 2.4°C by 2100:
We are currently between the two headed for about 3°C by 2100.
To explore how the climate changes for other cities in the US go here:
This is how they did it, a paler yellower green means a closer analogue.
For the low emissions scenario they found a good analogue, for the high emissions scenario, none of them were that good but they pick the best.
The paper is here
Every year, all the nations involved in the agreement meet to increase their pledges. So this year expect increased pledges from them. But not instantly to 1.5 °C. Some are already within 1.5 °C. Some even well within, right down to 1.2 °C and below. A couple are carbon negative, Bhutan and Suriname which is hugely carbon negative due to all its forests. Costa Rica should be carbon neutral by the early 2020s.
Amongst populous countries the biggest population on track to 2 °C already is India with a population of 1.4 billion. India also has 1.5 °C well within reach for future pledges.
China is on track for below 4 °C but it needs a huge ramp up in pledges needed to get down to 2 °C or 1.5 °C. However it had to build an entire new industry of renewables to get where it is now, has getting on for half the installed renewables in the world and is exporting the technology to other countries - it's been a good business move for them too. They also planted large forests to offset global warming. The IPCC report said that all four of its 1.5 °C scenarios required a degree of afforestation.
This map is from 2017, from before the US said they would withdraw, and a bit out of date, but it is the most complete one I can find. It shows what temperature rise each country’s pledge corresponds to if everyone did the same. It's interesting to click around. This is just a screenshot:
The actual map is here, and you can click on each country to see what it’s pledge amounts to by way of temperature rise: Paris Equity Check | Pledged Warming Map
The ones that are already close to 1.5 °C include Switzerland 1.6 °C, and Pakistan 1.2 °C is a good example from a rather populous country.
Many African countries are at 1.2 °C. Philippines, Peru and Ecuador all 1.2 °C. Guatemala and Costa Rica less than 1.2 °C. Indeed, many of the poorer countries are leading the way.
This is another map from Climate Action Tracker, again just a screenshot, and it doesn’t have complete coverage, but is more up to date:
Countries | Climate Action Tracker
Remember this is just the first of many yearly meetings. It's always been the plan that you have to start somewhere and they will do new more ambitious pledges.
Nor is it just that they increase them occasionally - the plan is to meet and increase their pledges each year. We don't expect them to reach 1.5 °C this time around
But in the next few years, they will be trying to increase on their previous pledges each year and more and more countries to get down to within 2 °C and then 1.5 °C.
That so many are already well within 1.5 °C - it is quite encouraging if you look at it another way.
India is the most populous of the countries on track to stay within 2 °C and with 1.5 °C also well within reach, with just short of 1.4 billion people, according to Climate Action Tracker
After adopting its final National Electricity Plan (NEP) earlier in 2018, India remains on track to overachieving its “2˚C compatible” rated Paris Agreement NDC climate action targets. Estimates show India could achieve part of its NDC goals—a 40% non-fossil-based power capacity by 2030—more than a decade earlier than targeted. But a question still remains over the future of coal.
If it were to abandon plans to build new coal-fired power plants, India could become a global climate leader with a “1.5˚C compatible” rating. This is more than feasible: the Draft National Electricity Plan contained no expansion of coal power after 2022. This scenario is supported by recent developments such as a 50% decrease in the cost of solar power in just two years and several utilities shelving plans for building coal plants. In 2017, renewable energy investment topped that of fossil fuel-related power investments. If the price of solar PV continues to fall, it stands to become the preferred choice for distribution companies. However, the final NEP took a backwards step of including more than 90 GW of planned coal-fired capacity—and these risk becoming stranded assets.
It is a particular challenge for China because it is rapidly industrializing but it is already on track to stay below 4 °C mainly due to its rapidly growing renewables industry, now amounting to nearly half the installed renewables in the world, with some of the largest solar power plants in the world. This is helping their economy too, as they are exporting the technology to other countries.
They are not on track for 2 °C. But they are a climate action leader in the world - it's like trying to reverse the direction of an oil tanker. They have tremendous momentum and it is a big thing just to stop, and then they have to reverse. The news reports often don't make this clear. It was never an expectation of the Paris agreement that the world could achieve pledges for 2 °C right away. The ones with the biggest challenges like China have to build up experience and capabilities first and entire new industries, before they have the ability to make the stronger pledges needed to stay within 2 °C and then 1.5 °C. The first thing is to stop the year on year emissions from increasing, and China is the key to that. Then they have to be reduced.
This is what Climate Action Tracker say about China:
China is positioning itself as a global climate leader, and its actions have an enormous impact on global greenhouse gas emissions. Discouragingly, a rise in coal consumption drove Chinese CO2 emissions to a new high in 2017, which will likely be exceeded again in 2018.
... The world’s largest emitter, China is simultaneously, and almost paradoxically, the largest consumer of coal and the largest solar technology manufacturer, and the choice it makes between the technology of the past versus the future will have a lasting effect on the world’s ability to limit warming to 1.5°C. China’s emissions, like the rest of the world’s, need to peak imminently, and then decline rapidly.
With current policies, CO2 emissions in China may level off in the next few years, but total greenhouse gas emissions are projected to rise until at least 2030.
Even so, China is on track to meet or exceed its 2030 Nationally Determined Contribution (NDC) , which the CAT rates “Highly insufficient.”
... Under current policies, China is also likely to achieve its (more stringent) 2020 target to limit fossil fuels, but neither of these targets are compatible with limiting global temperature increase to 1.5°C.
Given that China is on track to achieve or overachieve its climate targets, its next step as a global climate leader could be to set an example by submitting a strengthened NDC to the Paris Agreement by 2020. (For details on China’s NDC, see “pledges and targets” section)
China now produces low cost solar panels which are used throughout Asia, middle East and they continue to decrease in price and increase in efficiency year on year. As a result of its big push for solar power and its pledge to increase non fossil fuel power sources to 20% by 2030, News sources also say it may increase the renewables target for 2030 to 35% of electricity consumption (expand the Energy sources section here Current Policy Projections).
There are many other solar production facilities in Asia, for instance in the UAE, but it’s hard for them to compete with the low cost solar panels from China Solar manufacturing in the Arab region remains difficult, IRENA says
In the Middle East solar energy has dropped to below 3 cents per kilowatt hour in some places. It helps to have low cost land, and to have very sunny weather. Analysing these and other details of how they did it, similar reductions from the current 6 cents per kilowatt hour to 3 cents per kilowatt hour are possible in the US too. One of the US plants already quotes less than 3 cents per kilowatt hour without subsidies (there are 30% subsidies):
This is clearly going to feed into future pledges, with availability of low cost renewables making targets more easily achievable.
Some of the scary stories suggest that we won’t be able to feed everyone so I’d like to answer that first.
Food security is growing year on year. Most of the population increase is in Africa where the population is projected to increase fourfold from 1 - 4 billion, and the green revolution in the 1950s to 70s which saved billions from starvation with new methods of agriculture and improved varieties passed it by.
The US and China produce ten times the yields of crops from the same land area as Sub Saharan Africa.
Yields and Land Use in Agriculture
We also have a huge safety margin from meat eating. Although it is not likely to come to it, if the US and Brazil were to switch from growing feed crops for animals to growing crops for humans from the same ground, they alone could feed an extra 2.5 billion people (they are both beef cattle countries and grow a lot of crops just to feed to cows).
The worst case when it comes to feeding everyone is we have to go on rations as in WWII rationed to a few ounces of meat a week.
We could also feed twenty times as many people than even the most efficient crop growing in the US using the methods of space agriculture - fast turn around crops, hydroponics and artificial lighting.
So, no, nothing we can do can get us into a situation where it is impossible to feed everyone. But we are not likely to need to use rationing or biointensive agriculture or space agriculture. Projections suggest we can feed everyone with conventional agriculture, but it needs major improvements in crop yields in Africa to do that. And we can do that with the methods of the green revolution and reversing desertification.
For more on this see my
There is a lot of hyperbole again in journalistic stories about soil erosion.
Yes, there are problems with soil degradation but only in some parts of the world. For instance there is no soil degradation where I live, the Isle of Mull off the West coast of Scotland. The soil is growing not washing away and we are not talking about a future where there won’t be any soil in the UK. There are many places in the world where soils are growing (as is the normal situation) just as they are where I live.
There are some areas where it is a serious issue, especially in Africa, though there are some problems of soil erosion in most countries worldwide (even in the UK there are some places where there are issues of soil erosion) - and many measures are being put in place to stop soil erosion.
It is an important matter that needs to be addressed. It’s an essential part of food security, and also it makes a significant difference to global warming as a CO2 sink.
This is a symposium to be held in May
This is the FAO overview with various documents you can download
This is the 2015 summary
This is about a new program launched in 2018 to help with the situation in Africa
Soils are also relevant to climate change, a healthy soil takes up a lot of carbon and soil erosion leads to emissions of carbon into the atmosphere
This research found that if the CO2 levels got very high, this disspiates low clouds that form over sea and help to cool Earth down. When that happens then the temperature worldwide rather rapidly increases by 10 °C. This was rather a surprising result. But we are nowhere near that threshold.
Their model suggests that if we continued “business as usual” i.e. if we had never done the Paris agreement but just pressed ahead regardless, we’d reach those levels towards the end of this century, at 1300 ppm. But they go on to say that their model depends on a simplification of the real situation. In actuality it most likely wouldn’t happen until 1400 to 2200 ppm, which puts it quite a long way into the next century even with “business as usual”.
It is not a risk for us on our current path. But it helps understand why the Earth got rather hotter at times in the past than you’d expect from the levels of CO2.
What did the research about “cloudless skies” really show? by Robert Walker on Debunking Doomsday
Yes we are getting extinctions at a far higher rate than normal. But it is nowhere near a mass extinction yet. Just the start of a slide towards one that may play out towards the end of this century and in the 22nd century. Also we are not risking a major mass extinction like the Permian / Triassic one. The word “mass extinction” does not have a well defined threshold but I think many who read these stories think it means that there would be almost no animals, fish, trees, plants or insects left or hardly any. No it doesn’t mean that. It means fewer species of each but not a world without them.
Also we start with a much more varied collection of species than normal because the continents are spread out on different land masses with entire ecosystems only in Australia or only in South America or Africa. When they mix then some species go extinct but the mixed ecosystem ends up if anything often more diverse than they were before the introductions.
Also there is no way that our domesticated animals and plants will go extinct. We are not headed for a world without sheep, cats, dogs, honey bees, or fish. We could keep all those things even in space colonies without any ecosystems at all. We have seed banks and the seeds in those banks won’t go extinct either.
We also have an additional seed bank at Svalbard as an extra backup of all the world’s agricultural crops
Svalbard Global Seed Vault - Crop Trust
The seeds are preserved at -18 °C. It is buried deep in the permafrost. If the power failed it would go up to - 8 or - 7 °C after a few years, but even at that temperature most of the seeds would be viable for 20 to 30 years so you have lots of time to decide what to do if power doesn’t get restored. So it is a safe place for the world’s seeds.
There are seeds there to restore the world’s agriculture even if there were no other seeds left in the entire world. Not just the main crops but numerous wild varieties for each one. Our seed crops are not going to go extinct.
There are a few seeds that can’t be preserved like that, some tropical fruits such as mangos can’t be freeze dried and have to be grown every year.
Only the corals are at risk of actual destruction of an entire ecosystem. We are losing species but we are also preserving many habitats and species.
And we are saving many of the large iconic species too, we are losing some such as the northern white rhino sub species, may or may not be possible to save the species, but e.g. we have saved the whales and there is no immediate near future of the blue whale going extinct. There would have been if we hadn't acted. We have saved many other species that would be extinct already if it weren’t for the work we do to preserve them.
The extinction rate is higher than background but many ecosystems are actually becoming more diverse due to incoming species from other continents, meanwhile worldwide many countries are doing a lot to protect biodiversity.
The coral reefs are important for the fish and other creatures that depend on them. There are many other shallow water ecosystems in the sea. I cover a couple of the others here:
More on the coral reefs later in this page, see ACIDIFICATION OF THE OCEANS - WINNERS AND LOSERS
Kelp and seagrass would not be affected by the coral reefs in any way. They are independent systems and they do have vulnerable spots but only some places.
And we are doing lots to encourage and preserve biodiversity. We can and should do a lot more, but are already doing a lot.
You also get extinctions if you merge together two ecosystems that evolved separately. For instance, 54 million years from now Australia will crash into China.
From this video:
That would mix together Australian and Chinese species that had never encountered each other before (if it weren't for humans that is) - so that would then lead to many extinctions. But the resulting ecosystem would likely be richer than the separate ones are now.
One interesting biologist, Chris Thomas, as I say in my debunk, argues that this is a good analogy to most of what is going on right now. A similar thing is happening in our world to what happens when continents merge, except we are doing the merging by moving things about across the sea.
I go into this in more detail here
This was a non systematic study that hit the headlines.For the whole of China they only had one data point, for domestic honey bees! And they found the studies by searching for articles with “Declin*” in the subject line.
There was a much better report from the UN just a week or two later and they did find that crops are better pollinated if there are wild insects as well as the domesticated honey bees, and that if there are more pollinators the crop yields increase (obviously only for crops that require pollinators)..
They comment that climate changes would require pollinators to shift their geographic zones and that some species might struggle to do that with sufficient speed. And talk about how preserving pollinator diversity can help in a buffering role, meaning those effects are less significant for crops.
So yes, diversity of pollinators is important.
Later on in the section 4.3.4 Associated biodiversity for pollination they talk about insects in detail. They talk about some individual reports.
They mention the German study, which I covered before here:
They also mention that Germany has started an Action Program for Insect Protection which is here (you can use google translate to see it in English): Insektenschutz
In their review of insect trends then it was mixed - most habitats had both rising and decreasing populations reported except for grasslands grazed with livestock which did show a downward trend. This was a far more systematic review than that appalling study a week or two previously. Yet it didn't feature on the news at all, while the other one had interviews with the researchers who said ridiculous things such as that we are headed for a world without insects which simply makes no sense at all.
I did an article about the UN biodiversity report here and it is worth dipping into the full report as it has many case study stories and some are rather heartening - gives an idea of how much is being done worldwide to preserve biodiversity.
They found that insects were decreasing only on livestock grassland-based systems. Everywhere else, the countries reported stable or mixed trends (i.e. neither increasing, nor decreasing nor stable trends predominate).
The main causes of decline identified by the countries were pesticides, human induced habitat loss, fragmentation, and climate change. Amongst those reporting increasing trends were Nepal due to crop diversification, several European countries due to flower strips in and around fields (as a result of an agri-environmental scheme) and increases in forest area particularly planted forests. While logging, natural disasters such as hurricanes, invasive species, overgrazing in Argentina and undergrazing in Norway all were thought to have caused declines in numbers of pollinators. See the section ''Status and trends of pollination" on page 134.
They remark on the limited data for insects, but it is vastly better than that insects study that hit the news a week or so back.
They talk about many measures that countries are taking to help support pollination of their crops. For instance they cover Malaysia’s “stingless bees” project. These are a different species from honey bees that are adapted to tropical and subtropical species and are better able to pollinate their crops than traditional honey bees. And they do also produce honey. Stingless Bees - Facts, Information & Pictures
The government has promoted keeping of stingless bee colonies to help with pollination:
There are many more details there in the report about the many things countries worldwide are doing to encourage biodiversity. As well as UN recommendations of ways that they will be able to do more of this in the future.
If you read the report itself it is far from bleak and rather heartening to read about all these projects so many countries are involved in to protect biodiversity.
They talk about many countries who submitted reports to the UN on measures they are taking to ensure biodiversity as part of their food and agriculture policies. This table is from 5.2 Overview of management practices and approaches
Though only some of the countries submitted reports they all reported increasing trends for nearly all these measures to promote and protect biodiversity.
The report is reasonably optimistic about the future. Many countries implementing such practices for crops, but having problems getting them in place that need to be addressed. The report itself has identified many knowledge gaps and actions they need to take in the future.
This is their conclusion of the report:
Positive global developments include, on the one hand, growing awareness internationally of threats to the sustainability of food and agriculture, including those related to the loss of biodiversity, and on the other, upward trends in levels of adoption of various management practices that potentially contribute to the conservation and sustainable use of BFA. These developments need to be built upon by the global community. Knowledge gaps need to be filled, cooperation strengthened, including cross sectorally and internationally, and financial, human and technical resources mobilized. Effective legal and policy frameworks need to be put in place. The country-driven process of preparing The State of the World’s Biodiversity for Food and Agriculture has led to the identification of numerous gaps, needs and potential actions in the management of BFA. The next step is to take action. Over the years, the Commission on Genetic Resources for Food and Agriculture has overseen the development of global plans of action for genetic resources in the plant, animal and forest sectors. Implementation of these instruments needs to be stepped up. Consideration also needs to be given to how the international community can more effectively promote synergies in the management of all components of biodiversity, across these sectors and others, in the interests of a more sustainable food and agriculture.
The State of the World’s Biodiversity for Food and Agriculture 2019
More about it in my article here:
You often get articles saying we can’t do these things to curb CO2 emissions, because it is too expensive - so let’s look at that.
This study finds that indeed it is more expensive to stay within 2 °C than 3 °C and that 1.5 °C is more expensive than either. But the costs are not that high compared to other things we spend money on.
They estimate a total cost to the world economy of the unconditional NDC’s as $135 billion by 2030, if they assume conditions of slow economic growth, rapid population growth and high inequality.
It’s less than half of that however, if they make more sustainable socio-economic assumptions.
The conditional pledges that various of the developing countries have made where they pledge something dependent on financial help from wealthier countries amount to a total of $40 to $55 billion .
That’s for the 3 °C path we are already on. For 2 °C they estimate the cost as at least three times higher and for 1.5 °C, it’s 5–6 times higher.
However while spending tens of billions we are saving trillions:
Also even these costs are not that large compared to, for instance, the estimated cost of renewing the UK Trident submarine. According to CND it may be as much as over £200 billion
And modernizing and maintaining the US nuclear arsenal over the next 30 years will cost $1.2 trillion according to one estimate.
If we can afford nuclear weapons surely we can afford to pay for climate change mitigation.
And at the same time save us lots of money for the future so that we end up 3% wealthier in 2100, or about $30 trillion dollars better off than if we hadn’t done it according to that paper.
It seems a no brainer really.
It’s more a matter of how to find a way to get from here to there. If it is going to benefit us so much as a world economy, can we do it in a way that the benefits are linked close enough to the costs to circle around and feed back into the process?
There is another figure you see though, from the IPCC report in 2018. The summary for policy makers says that we will need to invest around $2.4 trillion extra in the energy sector. That may seem daunting at first:
“Global model pathways limiting global warming to 1.5°C are projected to involve the annual average investment needs in the energy system of around 2.4 trillion USD2010 between 2016 and 2035, representing about 2.5% of the world GDP (medium confidence).” 4.4.5, Box 4.8}
This is not quite the same thing though. It is investment for a return on the investment. This is a modest increase in investments we already do. It is explained in detail in chapter 4.4.5
The average increase of investment in the energy sector resulting from Box 4.8 represents a mean value of 1.5% of the total world investment compared with the baselines scenario in MER and a little over 1% in PPP. Including infrastructure investments would raise this to 2.5% and 1.7% respectively.
In other words we have to invest an extra 1.5% in the energy sector every year, over what we are doing at present. Or 2.5% including the infrastructure investments.
Meanwhile the fossil fuel assets we have already are decreasing in value. So it’s a case of investing more in green energy at the same time as fossil fuel assets decrease in value.
They say in their box 4.8
“ Part of the challenge may lie in increasing the pace of financing of low-emission assets to compensate for a possible 38% decrease, by 2035, in the value of fossil fuel assets (energy sector and indirect holdings in downstream uses like automobiles) (Mercure et al., 2018).”
Much of their chapter 4 is about how this might be achieved. It’s complex economics and I’m no economist but they clearly think it can be done.
What does this mean?
It doesn't make any difference to the predicted temperature changes as they don't use GWP100 for the modeling but directly model the effects of the methane. In their models they have as input the methane emissions for each year, and then they work out the temperatures from those directly by looking at the effects of that methane on the climate.
It makes a difference rather to policies, if you use GWP10 then countries that do rapid reductions in methane while keeping CO2 levels high will be seen as contributing more towards climate change mitigation in their NDC's.
It also changes the way you present the model. If you ask "for this model with these assumptions about methane emissions, when are net zero emissions achieved" then the time of net zero CO2 emissions is moved forwards but only by a few years on most of the scenarios. This makes no difference again to what happens to the temperature, to how the models respond to the emission changes, but the point at which you say to policy makers: "We have reached net zero" changes.
This is especially significant for policy if you do negative CO2 emissions to keep at net zero and target net zero emissions for the second half of the century. Whether you use GWP100 or GWP10 will change the targets of how much negative CO2 emissions you need to do.
If you target net 0 with GWP10 then you focus more on reducing methane to start with, so that then means a different projection with more rapid temperature effects early on. Use of GWP100 for net zero emissions comes closest to holding temperatures constant by maintaining net zero emissions.
The higher metric value for methane under GWP20 or GTP100 (another metric, based on temperature rather than warming potential but harder to calculate)) means you need to use more negative CO2 emissions to achieve a perceived net zero emissions and so you get a higher offset and so the temperatures actually decrease significantly within a few decades under a net zero with GWP20 would be even more with GWP10.
With this background, if your aim is to reach a steady temperature after net zero emissions use of GWP100 makes more sense.
If you want to come back to a lower temperature at that point use of GWP10 or GTP100 would make more sense.
This graph shows the difference, these are years after net zero emissions are achieved, they assume in the year 2100 and assume policies from then on maintain exactly net zero with the GWP100, GWP20 or GWP* a new metric the author proposes and various GTPs.
The GWP20 is in black and results in a net drop by over 0.7 °C in a century. The GWP100 is in orange and results in a drop of nearly 0.4 °C in a century both assuming you use those metrics as a basis for your policy of net zero emissions. It's of course using many different assumptions about the amount of methane emitted etc, the solid lines are an average.
The GWP* is a new metric proposed by the authors, which results in more or less constant temperature if you target net zero emissions using that metric. That's figure 5a from this paper from 2018
Implications of possible interpretations of ‘greenhouse gas balance’ in the Paris Agreement
Let’s look at a longer time period beyond 2100.
I already shared this graph but let’s share it again:
In this figure the blue line is the one that goes down to zero emissions quickly. It levels off at 1.5 °C above pre-industrial and then slowly goes down after that getting back to our current levels by a little after 2300. The red curve is “business as usual” in which emissions stay constant through to 2150 and after that CO2 concentrations stay constant (the rationale being there just aren’t enough resources available to keep burning fossil fuel endlessly):
The RCP greenhouse gas concentrations and their extensions from 1765 to 2300
Even that red graph will not make Earth uninhabitable to humans. There will still be ice at both poles, with the Antarctic and Greenland ice taking thousands of years to melt. And as the world warms up then parts of Siberia and Canada open up to conventional agriculture.
It is much more a case of climate migration, of people moving from one part of the world to another. We could feed as many people. There is a lot of leeway here. With biointensive agriculture we could feed ten times as many people and with space agriculture methods using mainly crops with a very rapid turnaround time of 30 days and hydroponics / aeroponics and artificial lighting you can feed a hundred people from an acre ,which under conventional agriculture can only feed one person.
But we don’t need that even. There is a lot of improvement possible with inefficient agriculture especially in Africa which has missed the green revolution that saved billions from starvation in the 2050s to 70s. For more on this see my
However, I think we can forget about “business as usual” since we are not on that pathway. So I won’t go into this any more here.
Apparently many people guess this wrong - how long do you think it takes for all the ice in Greenland to melt if we continue with the same CO2 emissions as we have today until we run out of fossil fuels?
The rightmost drawing here with all the ice melted is not 2100, it's the year 3000.
Image credit: UAF Geophysical Institute
It is not certain even then. Between 72 and 100% lost according to a recent study.
That’s “Business as usual”, i.e. continuing to burn fossil fuels as we are now, with no reductions in CO2 emissions at all through to the 23rd century, eventually stopping mainly because we run out of fuels to burn.
We are nowhere near that path even with the pledges so far. We would be well below it just from competition from renewables, with prices for new renewables based power stations continuing to fall rapidly every year.
This shows the ice sheet for the year 3000 under three scenarios - I’ve added extra labels with the projected temperatures by 2100 since that’s much better known than the RCP numbers:
Contribution of the Greenland Ice Sheet to sea level over the next millennium
There the amount of ice lost and the sea level rise by 2300 are
As a table with a few more sea levels for 2200 and 2300
| Temperature by 2100 | 2100 | 2200 | 2300 | 3000 | Ice loss by 3000 |
|---|---|---|---|---|---|
| 1.5°C (RCP 2.6) | 0.05–0.19 m |
0.11–0.37 m |
0.17–0.55 m |
0.59–1.91 m |
8 to 25% |
| 2.4°C (RCP 4.5) | 0.08–0.23 m |
0.20–0.57 m |
0.35–0.97 m |
1.97–4.16 m |
26 to 57% |
| 4.9°C (RCP 8.5) | 0.14–0.33 m |
0.52–1.55 m |
0.94–3.74 m |
5.38–7.28 m |
72 to 100% |
There the range is for 16% probability through to 84% probability
There the last one, the “Business as usual” or RCP 8.5 is using the extended RCPs so that would mean that it’s burning fossil fuels just as we are now all the way through to 2200 when it finally stops because we are just about out of fossil fuels. Here the orange RCP 6.0 or 3°C is roughly what we are on right now with the climate pledges so far.
This shows what happens to the temperature - as measured from 2000, not from pre-industrial - from pre-industrial it is a degree higher:
Here the idea is that for all the pathways except the lowest, the 1.5°C one ,then once the target CO2 level is reached a small amount of anthropogenic emissions continues, just enough to keep the CO2 levels at that constant level.
Those graphs are from another earlier study:
The RCP greenhouse gas concentrations and their extensions from 1765 to 2300
We are well below this scenario RCP 8.5. It’s an exceedingly unlikely, indeed impossible case. Even just through commercial competition of renewables we can’t end up there.
For more on why RCP 8.5, or “business as usual” is impossible and about the situation we are in at present with current pledges:
Contribution of the Greenland Ice Sheet to sea level over the next millennium
Also, the IPCC in its 2018 example of a worst case scenario did not find it credible that we could get through to 2100 without any attempts to reduce emissions even if we were somehow to abandon the Paris agreement in 2018 (which didn’t happen).
See The IPCC’s own worst case climate change example - a 3°C rise by 2100
The world population is set to level off by 2100 and most of the rise in population is in Africa. Due to prosperity rather than scarcity.
It’s the most prosperous countries that have declining populations, such as Japan. Our population is leveling off due to prosperity rather than scarcity.
We reached close to peak child about a decade ago, number of children is still slightly increasing year on year but hardly at all, most of the increase is due to a dramatic increase in life expectancy, by 20 years in the last half century in the developing world and by ten years in the developed world. In some places it’s even more, 30 years.
Life expectancy is increasing for all age groups, most for the younger children and newborns - this is for England and Wales:
Although it is a challenge to feed another four billion people we can definitely do it. We could in worst case do it just by rationing meat in the more developed countries, but it is not likely that it comes to that. And the population may well level off before then, Africa is the key, a four-fold increase in its population is a big increase and it may not happen if they can move to prosperity and higher levels of education sooner. Whether our world population in 2100 is well over or well under ten billion mainly depends on what happens in Africa.
What will make the difference is not scarcity but the opposite, improvements in education of women, their opportunities in the job market and the pace of improvements in child health.
The UN projects a population [in Africa] of 4.5 billion while WC-IIASA projects a population of only 2.6 billion. This difference of 2 billion is just as large as the difference between the projection for the global population by the UN (11.2 billion in 2100) and WC-IIASA (8.9 billion in 2100). Whether the world population increases to more than 10 billion will be decided by the speed with which Africa develops – especially how quickly women get access to better education, women's opportunities within the job market, and how rapidly the improvements in child health continue.
For more on this:
Our climate is particularly stable right now, apart from the human warming. During the last ice age there were many abrupt changes in climate. Interglacials are more stable than ice ages. This is a study of a site called Star Carr - Wikipedia in East Yorkshire:
Yet these early societies were well able to withstand the stresses of sudden abrupt climate change
We show that—once established—there was intensive human activity at the site for several hundred years when the community was subject to multiple, severe, abrupt climate events that impacted air temperatures, the landscape and the ecosystem of the region. However, these results show that occupation and activity at the site persisted regardless of the environmental stresses experienced by this society. The Star Carr population displayed a high level of resilience to climate change, suggesting that postglacial populations were not necessarily held hostage to the flickering switch of climate change. Instead, we show that local, intrinsic changes in the wetland environment were more significant in determining human activity than the large-scale abrupt early Holocene climate events.
The resilience of postglacial hunter-gatherers to abrupt climate change
On the other hand climate change may have played a roll in some previous cases of civilization collapse.
An example here is the late bronze age civilization in the Eastern Mediterranean, which mysteriously collapsed around 3200 years ago. It may have been the result of a 300 year drought:
The Late Bronze Age world of the Eastern Mediterranean, a rich linkage of Aegean, Egyptian, Syro-Palestinian, and Hittite civilizations, collapsed famously 3200 years ago and has remained one of the mysteries of the ancient world since the event’s retrieval began in the late 19th century AD,”
“By combining data from coastal Cyprus and coastal Syria, this study shows that the Late Bronze Age crisis coincided with the onset of a 300-year drought event 3200 years ago. This climate shift caused crop failures, dearth and famine, which precipitated or hastened socio-economic crises and forced regional human migrations at the end of the Late Bronze Age in the Eastern Mediterranean and southwest Asia.”
“Although we are probably better equipped than ever to predict the effects of climate change upon a particular location, we should never assume that our knowledge is complete, nor that we are fully prepared for the changes to come.” Climate change hastened ancient civilizations' collapse: study
We of course have far more resources than them, high level of literacy, and a great deal of knowledge to draw on. But we may need all of that to be resilient to climate change.
This is another study of abrupt events at 9.2 and 8.2 thousand years ago in southern Asian which came to the conclusion that they were very resilient
We assess the impacts of the 9.2 and 8.2 ka BP climate events on Southwest Asian farming communities
- We use over 3000 quality-checked 14C-dates in combination with archaeological evidence
- No large-scale collapse/decline or migration took place at around 9250 or 8200 cal BP
- There is some evidence for local adaptation, but not at all sites
- Early farming communities in Southwest Asia were resilient to rapid climate change
What we do find in the literature are many studies of climate change resilience. The message is that new methods are needed to make agriculture more resilient. Farmers are having to be more creative.
There we can make a distinction from Climate Change Adaptation, where you adapt to a change that has already happened and Climate Change Resilience, where you build in a resilience to future changes.
Let’s look at a couple of examples.
Mamadou Oussei, director of Aoulaye Sesame which grows white sesame seeds in Niger, has planted trees alongside the sesame to help keep the farm green and adapt to increasing droughts.
However they also had intense rainfall and flooding, so he is now considering planting cassava, a more water tolerant crop, so that if the sesame crops fail due to excessive water he still has the cassava crop.
For another example, then in the US, many fruit farmers are running into the problem that with warmer winters, the trees blossom earlier, and sadly, often before the last frosts of the year. The roots and twigs are very resistant to cold, but the blossoms are not, becoming increasingly sensitive to the cold as the bud breaks and then the flower opens.
Many of the fruit trees need to be chilled in winter to fruit - and if they don’t get cold enough they produce less fruit.
Then - if the winter is too warm, the blossoms form too soon and then they fall off after a late spring frost.
The problem is that the trees have a blossoming and fruiting cycle that doesn’t match the climate. So they need to breed new varieties that, for instance, will blossom later. But a new variety of fruit tree can take several decades to develop, just because the lifetime of a tree is so long. Another possibility is to grow new kinds of fruit - much like the way in the UK grapes are now being grown in the south of England.
However meanwhile some are using mitigation methods to grow the same fruit as before, but protecting them from the frost. That’s mentioned in this podcast:
Climate Change and Fruit Trees | Orchard People
at 18:00 in - after mentioning breeding and new varieties he goes on to talk about some cultural management strategies to help prevent the amount of damage we have from spring frost
There are many groups involved in working on climate resilience
For the US:
For the World Population Fund
Building on the INFORM framework and index, UNFPA developed a Population Risk and Resilience Assessment Framework, and a tool (DECA) to consolidate information essential for building resilience and sustainability in communities, and particularly among women and girls. The framework aligns UNFPA’s targeted vulnerable population with disaster risk reduction and climate change adaptation, and complements INFORM by adding a demographic perspective. This approach has been applied in a range of countries, including Malawi and Indonesia.
A Framework for the Assessment of Population Risk and Resilience to Climate Change
The Wikipedia article on this seems reasonable and worth linking to:
Well eventually, with "business as usual", the Greenland ice sheet is likely to melt completely leading to a sea level rise of 7 meters average, and much higher in some parts of the world. The threshold for this to happen is probably less than 4 °C relative to pre-industrial and it may happen even with a 1 °C rise. But this is likely to take a thousand years (it takes a long time to melt all that ice).
What about the nearer future, in the 22nd century?
In these new studies, a team of glaciologists using satellite and air measurements say that the ice in Western Antarctica has already started a process that is probably impossible to stop. With ice penetrating satellite radar mapping of the terrain beneath the ice (using the EU Sentinel 1 satellites), they say that here are no mountains or hills significant enough to slow the collapse. The fastest melting glacier, Smith glacier, is losing 70 meters thickness of ice a year. It's grounding line - the point at which it starts to float on the sea - is retreating two kilometers a year and has been doing that since 2011, is continuing unabated.
There are six glaciers that will collapse, enough to raise the sea level another four feet. But these may collapse other glacier leading to a rise of sea levels triple that. A separate team studying just one of the glaciers, Thwaite glacier, came to the same conclusion that collapse is inevitable. That is, will happen anyway, based on the CO2 emissions so far.
Our climate is predictable over such long timescales that they can even calculate when the next ice age will be - with or without CO2 warming - different dates for the two cases - though over shorter timescales you of course still can't predict every heat wave and hurricane.
Usually an interglacial like ours lasts for only around 10,000 years. It's 11,500 years since the last ice age. The amount of sunshine we receive in the northerly 65 degrees latitude is close to its minimum for the Milankovitch cycles. That would normally mean that we would be headed for an ice age already. But we aren't. Why is that?
In a recent study the authors selected only the models that most accurately tracked the previous ice ages, and used that to study whether or not we are due to plunge into the next ice age. They found that if they ran the models with CO2 levels of 240 ppm, similar to the Halocene, then the next ice age would be as soon as 1500 years into the future.
But if they used the pre-industrial levels of CO2 of 280 ppm, then the next ice ages should be 50,000 and 90,000 years from now (with a possibility of a slowly approaching ice age 20,000 years from now). Just that extra 40 ppm made all the difference. They are unsure why we had more CO2 this time around. Perhaps human activity even in pre-industrial society was enough to raise the levels by 40 ppm, which isn't very much, or at least contributed to the levels.
They found that with 500 Gt of emissions, not far off what we have already reached, we may already have enough CO2 in the atmosphere to make a difference to the ice sheets over thousands of years. If it reaches 1000 GT then the chance of an ice age in the next 100,000 years is notably reduced and with 1500 GT of emissions then it is very unlikely that we get an ice age in the next 100,000 years. And with higher levels of emissions, then we will end the pattern of ice ages altogether. You can read it in full under Nature's sharing initiative if you click on the link " published in the journal Nature" in the article in the Guardian here: Fossil fuel burning 'postponing next ice age
In that paper, they say
" Using an ensemble of simulations generated by an Earth system model of intermediate complexity constrained by palaeoclimatic data, we suggest that glacial inception was narrowly missed before the beginning of the Industrial Revolution. The missed inception can be accounted for by the combined effect of relatively high late-Holocene CO2 concentrations and the low orbital eccentricity of the Earth7. Additionally, our analysis suggests that even in the absence of human perturbations no substantial build-up of ice sheets would occur within the next several thousand years and that the current interglacial would probably last for another 50,000 years."
So in other words yes, we were due to go into an ice age around the start of the industrial Revolution, but it's not just the CO2 that stopped it. The various cycles are complex with many factors interacting and their analysis suggests that this time around the interglacial would have lasted 50,000 years anyway.
Their crucial graph is this one on page 203 of the paper.
The graph at the top shows the effects of different levels of CO2 now over the next 100,000 years plus in black, variations in amount of sunlight. The graph at the bottom shows the amount of ice in red, orange or blue with the colour there matched to the colour of the curve in the top half of the graph.
Notice that there's a significant difference between the predictions of the amount of ice, depending on the levels we reach in the near future, even 100,000 years from now.
With all the scenarios, there is much less CO2 of course 100,000 years in the future, but you still see differences because the amount you have then if we get to 1000 gigatons this century is still double the amount you get if we don't go above 500 gigatons. Apparently even that small amount of CO2 is enough to be significant. The reason is that the way carbon dioxide behaves in the atmosphere is very complex.
(see . CLIMATE CHANGE - the IPCC scientific assessment)
For instance after adding a pulse of CO2 to the atmosphere,
So for example, of the roughly 32 billion tons of CO2 that humans added to the atmosphere in 2010
That 15% which is left after thousands of years with a long term half life of 13,500 years is enough to prevent the next ice age and possibly, depending how much CO2 we add in total, end the cycle of ice ages altogether.
It's not so bad at all to have prevented the next ice age. The climate is much more stable during the interglacials, while during ice ages then you can get dramatic changes of climate within decades. Also the Earth is more habitable for us during the interglacials.
If the climate gets too hot then we could be headed for a hothouse Earth. If it weren’t for the CO2 emissions we’d be headed for a new ice age eventually thousands of years into the future. As is then so long as we can stop emissions some time this century we should be headed for a reasonably comfortable intermediate state, which could keep our climate stable and comfortable for humans for tens of thousands of years into the future.
Also
I briefly mentioned the NASA asteroid warnings, on those see my
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Added new sections:
Added extra paragraph about plummeting solar panel prices to Paris pledges so far
Added more up to date Climate Tracker map to Yes we can feed everyone and explained the other one is from 2017
