I think it is a very hard area to provide an accurate outline of, and I think to do that you need to go beyond reading the abstracts of papers and to look at the assumptions in those paper which typically combine very pessimistic warming, very pessimistic economic growth, limited or no adaptation. I think a lot of your analysis errs in a pessimistic direction.
[edit: misread the first point]: “The IPCC’s 6th Assessment Report predicts that, even if we fail to undertake significant further action, it’s very unlikely that we’ll reach 3°C or more of warming.” I’m not sure where you are getting this from given that you direct the reader to a >3000 page report, but this is now widely accepted to not be true. As I discussed in my report on climate change, warming of 2.5C is widely accepted to be the most likely outcome on current policy by a range of modelling studies. Since this does not account for changes in policy, this is pessimistic.
It is notable that you ignore climate economics in your overview. This is the field tasked with estimating the aggregate costs of climate change, and most models find that the costs of warming for 2-3C are a 0-5% reduction of GDP relative to a world without warming. Since GDP per capita will increase several fold up to 2100, average living standards will still be higher. These models do not find that the costs of 1.5C would be ‘huge’, rather that they are close to a 0% reduction in GDP. Given that we are already pretty close to 1.5C, it is pretty obvious that the effects will not be ‘huge’ (but I’m not sure what you mean by that).
Do you disagree with these models? If so, why? The best ones include the impacts you talk about here, including food, flooding drought, heat stress etc, and find the same results. I don’t think you should be selective in accepting the expert consensus on things without evidence or argument.
You say that climate change will increase food insecurity. True, but studies that incorporate the effects of climate change, economic growth and agricultural progress find reductions in food insecurity on nearly all socioeconomic scenarios. I think it would be worth providing this context.
Drought
You cite the carbonbrief article on people subject to drought which, for those who can be bothered to check, cites this article, which does not consider adaptation in its estimates and so is not realistic.
You cite the study saying that 132 million extra people will be exposed to drought in a 1.5C world. We are already nearly in that world and this decadea total of 662 people have died from drought per year, according to Our World in Data. This would be useful context.
Water scarcity is mainly driven by mispricing of water and especially subsidies of water for farmers.
Temperature-related deaths
You say that at 1.5C “nearly 14% of the world’s population could experience severe heatwaves at least every five years”. Yes, but we are nearly in that world today, and today cold-related deaths are 9x heat-related deaths (Zhao et al 2019). In the near-term at least we should expect temperature-related deaths to decline due to climate change. I think you should at least note this in your overview.
You cite Bressler et al (2023). Bressler et al claim that assuming limited adaptation, very pessimistic economic growth (SSP3) and very pessimistic warming (RCP8.5), deaths increase by 5 million per year by 2100. Per the IPCC, it is not actually permitted to combine SSP3 and RCP8.5, but studies often do this. Bressler et al also doesn’t consider many important forms of adaptation, which have led to declining heat-related deaths in rich countries. Consequently, I think the estimates in Bressler et al are not accurate, at least biased high by several orders of magnitude and probably have the wrong sign.
Tipping points
You note the release of vast amounts of methane from the Arctic. There is one study asserting without evidence that this would happen, but it is extremely controversial and expert elicitation suggests that methane clathrates would increase 2100 temperatures by at most 0.1C on an insanely pessimistic emissions scenario (RCP8.5).
You cite the Kemp et al study claiming “sudden, severe, and potentially irreversible changes to the climate” but they don’t provide any evidence for this and the IPCC denies this, if you mean “an shift in global climate that happens due to warming before 4C that adds more than 2C to global temperatures”. The main argument provided in the Kemp paper is a causal loop diagram with a lot of arrows running between climate change and other problems. It is notable that one could apply the same analysis to other things such as ‘bad economic policy’ without arriving at the conclusion that this is a serious catastrophic risk.
In general, if you are defining ‘catastrophic risk’ in the usual way, could you explain how you get to >800 million deaths from climate change via a non-conflict pathway? The biggest death estimate for a particular impact I have seen is the Bressler et al claim that assuming limited adaptation, very pessimistic economic growth (SSP3) and very pessimistic warming (RCP8.5), deaths increase by 5 million per year by 2100. (Per the IPCC, it is not actually permitted to combine SSP3 and RCP8.5, but studies often do this.) On more plausible assumptions, I would expect temperature-related deaths to decline. Even if you take the Bressler estimate at face value, where do you get the remaining >795 million deaths? For all other impact pathways I have seen, deaths from weather-related events are set to decline relative to today due to economic growth and adaptation.
Conflict
In support of the claim that climate change is an important contributor to conflict risk you cite an 80,000 Hours article. The IPCC is highly equivocal on the effects of climate change on civil conflict. It basically says nothing about the effects on interstate conflict and no scholars of great power war think it is an important driver of 21st century potential great power conflicts.
Thanks for these comments! Really appreciate the time you taking the time to give such thorough feedback. Needless to say, there’s quite a lot to think about here (both in terms of where updates to the content might be warranted and where we might stand by the original claims). I’ll give my thoughts when I’m able to, likely in the next few days.
Again, I want to thank you for the feedback you’ve given. We really appreciate engagement with the content, including meaningful critical engagement.
Given the volume of comments you had, I’m not going to provide too much in the way of object-level discussion (with one exception in a reply below). However, I think there are two important overall takeaways:
1: Many points you raise give important context and nuance, and in some cases importantly different headline conclusions. With these comments in mind, as well as further research, we’re going to revisit the content and make changes where we think it’s appropriate. It’s highly likely we’ll conclude that some changes are warranted – for instance (but not exhaustively), by clarifying where we’re giving figures conditional on more severe emissions scenarios, and discussing the effect economic growth is likely to have on strengthening adaptation. I think the content will be more accurate as a result of your comments, so thank you!
2: It’s possible someone who has just read the comments on this post could come away with the impression that each of these criticisms reflects an inaccuracy with our content, which we don’t think would be a correct inference. In some cases, we’re either already aware of the nuances you’ve raised, don’t think they give us sufficient reason to update our content, or don’t think they necessarily represent claims we’ve made.
For example, in a comment below you imply that we exaggerate the importance of wildfires. I don’t think this is a fair characterisation; not only do we exclude wildfires from our priorities article, we devote only one word to them in our climate overview. We mention them only to note that they are expected to increase in frequency due to climate change (which is true). Additionally, we believe you substantially underestimate of the mortality impacts of wildfires. I discuss this in a reply below. Here are a few quick smaller points:
You say that climate change will increase food insecurity. True, but studies that incorporate the effects of climate change, economic growth and agricultural progress find reductions in food insecurity on nearly all socioeconomic scenarios. I think it would be worth providing this context.
Agreed—we discuss this in our article on climate change priorities. It might also be worth mentioning in the overview.
In support of the claim that climate change is an important contributor to conflict risk you cite an 80,000 Hours article. The IPCC is highly equivocal on the effects of climate change on civil conflict. It basically says nothing about the effects on interstate conflict and no scholars of great power war think it is an important driver of 21st century potential great power conflicts.
I think the wording of this point implies we have more confidence in this dynamic than we state in the article. Just for reference, our phrasing of this point is ‘On top of this, some are also concerned that the effects of climate change may indirectly exacerbate other large-scale risks, too – such as increasing the chance of international conflict… These considerations increase the importance of climate change beyond its direct effects’. This isn’t intended to (and hopefully doesn’t) convey a high probability of climate change leading to great power war – though I understand that more context and additional caveating would likely be beneficial.
To characterise the trend in flood deaths as anything other than a dramatic downward trend seems clearly wrong.
If you’re referring to my comment, my claim was that ‘annual flood deaths have been fairly flat since the 1970s.’ I think this is a pretty fair extrapolation from the OWID data, given that we’re talking about absolute mortality numbers and not the average lethality of each flood event!
On a general note, as a small organization we have limited capacity and expertise of our own. This means we rely on deference to both respected institutions and mainstream resources more than we otherwise might. I think this deference is typically justified, though there are many obvious caveats. Regardless, pointing us towards specific points (or more general claims) you believe are suspect as well as resources that raise valid disputes helps us to better evaluate contentious claims—so we appreciate that.
Hi Dylan, thanks a lot for these thoughts I appreciate the openness to criticism a lot. As I mentioned, I think it is extremely difficult to provide a good overview of this topic in part because the literature is so vast. A draft I wrote on climate change a couple of years ago was correctly described as ‘drivel’ by a climate scientist a couple of years ago; I think any assessment of the quality of work on this topic should be forgiving especially when researchers are pushed for time. Some professional scientists think that 3-4 degrees of warming will kill billions of people due to food loss and heat stress, whereas myself and others think this is clearly wrong. I think there is, as lots of people seem to want to say nowadays, a lot of ‘misinformation’ about climate change. Scientists and media organisations who claim that ‘misinformation’ is one of the great problems of our time don’t seem to care about ‘misinformation’ on climate change. One can speculate as to why this might be.
I may be biased, but my report on climate change might be useful. I’d also be happy to provide feedback on any future drafts.
On floods: firstly, I think the per capita death rate is the best metric for assessing whether weather events themselves are getting worse. The global population has increased by 4.3 billion people since 1970 (and there is large net migration to coastal regions). So, attributing all of the increase in flood deaths to changes in weather trends is wrong. The death rate is the measure we should use. Second, the trend in per capita deaths from floods is down.
On wildfires I agree that the indirect effects look more important than the direct effects. However, one also has to consider whether there is a trend in wildfires, what it is, and to what extent it can be attributed to climate change. I think there is considerable doubt about all of these issues, as discussed by Roger Pielke here. As I noted above, the IPCC has low confidence in any trend in fire weather, i.e. the weather conditions that might contribute to wild fires.
Is there a trend in wild fires? Yes, it appears to be downward since 2003.
Canada, which was recently the subject of a lot of attention about wildfires has seen a declining/flat trend since the 1990s. Claims that climate change is driving the non-existent upward trend is presented in the Guardian, New York Times, and NPR.
I think it is a very hard area to provide an accurate outline of, and I think to do that you need to go beyond reading the abstracts of papers and to look at the assumptions in those paper which typically combine very pessimistic warming, very pessimistic economic growth, limited or no adaptation. I think a lot of your analysis errs in a pessimistic direction.
[edit: misread the first point]: “The IPCC’s 6th Assessment Reportpredicts that, even if we fail to undertake significant further action, it’s very unlikely that we’ll reach 3°C or more of warming.” I’m not sure where you are getting this from given that you direct the reader to a >3000 page report, but this is now widely accepted to not be true. As I discussed in my report on climate change, warming of 2.5C is widely accepted to be the most likely outcome on current policy by a range of modelling studies. Since this does not account for changes in policy, this is pessimistic.It is notable that you ignore climate economics in your overview. This is the field tasked with estimating the aggregate costs of climate change, and most models find that the costs of warming for 2-3C are a 0-5% reduction of GDP relative to a world without warming. Since GDP per capita will increase several fold up to 2100, average living standards will still be higher. These models do not find that the costs of 1.5C would be ‘huge’, rather that they are close to a 0% reduction in GDP. Given that we are already pretty close to 1.5C, it is pretty obvious that the effects will not be ‘huge’ (but I’m not sure what you mean by that).
Do you disagree with these models? If so, why? The best ones include the impacts you talk about here, including food, flooding drought, heat stress etc, and find the same results. I don’t think you should be selective in accepting the expert consensus on things without evidence or argument.
You say that climate change will increase food insecurity. True, but studies that incorporate the effects of climate change, economic growth and agricultural progress find reductions in food insecurity on nearly all socioeconomic scenarios. I think it would be worth providing this context.
Drought
You cite the carbonbrief article on people subject to drought which, for those who can be bothered to check, cites this article, which does not consider adaptation in its estimates and so is not realistic.
You cite the study saying that 132 million extra people will be exposed to drought in a 1.5C world. We are already nearly in that world and this decade a total of 662 people have died from drought per year, according to Our World in Data. This would be useful context.
Water scarcity is mainly driven by mispricing of water and especially subsidies of water for farmers.
Temperature-related deaths
You say that at 1.5C “nearly 14% of the world’s population could experience severe heatwaves at least every five years”. Yes, but we are nearly in that world today, and today cold-related deaths are 9x heat-related deaths (Zhao et al 2019). In the near-term at least we should expect temperature-related deaths to decline due to climate change. I think you should at least note this in your overview.
You cite Bressler et al (2023). Bressler et al claim that assuming limited adaptation, very pessimistic economic growth (SSP3) and very pessimistic warming (RCP8.5), deaths increase by 5 million per year by 2100. Per the IPCC, it is not actually permitted to combine SSP3 and RCP8.5, but studies often do this. Bressler et al also doesn’t consider many important forms of adaptation, which have led to declining heat-related deaths in rich countries. Consequently, I think the estimates in Bressler et al are not accurate, at least biased high by several orders of magnitude and probably have the wrong sign.
Tipping points
You note the release of vast amounts of methane from the Arctic. There is one study asserting without evidence that this would happen, but it is extremely controversial and expert elicitation suggests that methane clathrates would increase 2100 temperatures by at most 0.1C on an insanely pessimistic emissions scenario (RCP8.5).
You cite the Kemp et al study claiming “sudden, severe, and potentially irreversible changes to the climate” but they don’t provide any evidence for this and the IPCC denies this, if you mean “an shift in global climate that happens due to warming before 4C that adds more than 2C to global temperatures”. The main argument provided in the Kemp paper is a causal loop diagram with a lot of arrows running between climate change and other problems. It is notable that one could apply the same analysis to other things such as ‘bad economic policy’ without arriving at the conclusion that this is a serious catastrophic risk.
In general, if you are defining ‘catastrophic risk’ in the usual way, could you explain how you get to >800 million deaths from climate change via a non-conflict pathway? The biggest death estimate for a particular impact I have seen is the Bressler et al claim that assuming limited adaptation, very pessimistic economic growth (SSP3) and very pessimistic warming (RCP8.5), deaths increase by 5 million per year by 2100. (Per the IPCC, it is not actually permitted to combine SSP3 and RCP8.5, but studies often do this.) On more plausible assumptions, I would expect temperature-related deaths to decline. Even if you take the Bressler estimate at face value, where do you get the remaining >795 million deaths? For all other impact pathways I have seen, deaths from weather-related events are set to decline relative to today due to economic growth and adaptation.
Conflict
In support of the claim that climate change is an important contributor to conflict risk you cite an 80,000 Hours article. The IPCC is highly equivocal on the effects of climate change on civil conflict. It basically says nothing about the effects on interstate conflict and no scholars of great power war think it is an important driver of 21st century potential great power conflicts.
Thanks for these comments! Really appreciate the time you taking the time to give such thorough feedback. Needless to say, there’s quite a lot to think about here (both in terms of where updates to the content might be warranted and where we might stand by the original claims). I’ll give my thoughts when I’m able to, likely in the next few days.
Hi John,
Again, I want to thank you for the feedback you’ve given. We really appreciate engagement with the content, including meaningful critical engagement.
Given the volume of comments you had, I’m not going to provide too much in the way of object-level discussion (with one exception in a reply below). However, I think there are two important overall takeaways:
1: Many points you raise give important context and nuance, and in some cases importantly different headline conclusions. With these comments in mind, as well as further research, we’re going to revisit the content and make changes where we think it’s appropriate. It’s highly likely we’ll conclude that some changes are warranted – for instance (but not exhaustively), by clarifying where we’re giving figures conditional on more severe emissions scenarios, and discussing the effect economic growth is likely to have on strengthening adaptation. I think the content will be more accurate as a result of your comments, so thank you!
2: It’s possible someone who has just read the comments on this post could come away with the impression that each of these criticisms reflects an inaccuracy with our content, which we don’t think would be a correct inference. In some cases, we’re either already aware of the nuances you’ve raised, don’t think they give us sufficient reason to update our content, or don’t think they necessarily represent claims we’ve made.
For example, in a comment below you imply that we exaggerate the importance of wildfires. I don’t think this is a fair characterisation; not only do we exclude wildfires from our priorities article, we devote only one word to them in our climate overview. We mention them only to note that they are expected to increase in frequency due to climate change (which is true). Additionally, we believe you substantially underestimate of the mortality impacts of wildfires. I discuss this in a reply below. Here are a few quick smaller points:
Agreed—we discuss this in our article on climate change priorities. It might also be worth mentioning in the overview.
I think the wording of this point implies we have more confidence in this dynamic than we state in the article. Just for reference, our phrasing of this point is ‘On top of this, some are also concerned that the effects of climate change may indirectly exacerbate other large-scale risks, too – such as increasing the chance of international conflict… These considerations increase the importance of climate change beyond its direct effects’. This isn’t intended to (and hopefully doesn’t) convey a high probability of climate change leading to great power war – though I understand that more context and additional caveating would likely be beneficial.
If you’re referring to my comment, my claim was that ‘annual flood deaths have been fairly flat since the 1970s.’ I think this is a pretty fair extrapolation from the OWID data, given that we’re talking about absolute mortality numbers and not the average lethality of each flood event!
On a general note, as a small organization we have limited capacity and expertise of our own. This means we rely on deference to both respected institutions and mainstream resources more than we otherwise might. I think this deference is typically justified, though there are many obvious caveats. Regardless, pointing us towards specific points (or more general claims) you believe are suspect as well as resources that raise valid disputes helps us to better evaluate contentious claims—so we appreciate that.
Hi Dylan, thanks a lot for these thoughts I appreciate the openness to criticism a lot. As I mentioned, I think it is extremely difficult to provide a good overview of this topic in part because the literature is so vast. A draft I wrote on climate change a couple of years ago was correctly described as ‘drivel’ by a climate scientist a couple of years ago; I think any assessment of the quality of work on this topic should be forgiving especially when researchers are pushed for time. Some professional scientists think that 3-4 degrees of warming will kill billions of people due to food loss and heat stress, whereas myself and others think this is clearly wrong. I think there is, as lots of people seem to want to say nowadays, a lot of ‘misinformation’ about climate change. Scientists and media organisations who claim that ‘misinformation’ is one of the great problems of our time don’t seem to care about ‘misinformation’ on climate change. One can speculate as to why this might be.
I may be biased, but my report on climate change might be useful. I’d also be happy to provide feedback on any future drafts.
On floods: firstly, I think the per capita death rate is the best metric for assessing whether weather events themselves are getting worse. The global population has increased by 4.3 billion people since 1970 (and there is large net migration to coastal regions). So, attributing all of the increase in flood deaths to changes in weather trends is wrong. The death rate is the measure we should use. Second, the trend in per capita deaths from floods is down.
On wildfires I agree that the indirect effects look more important than the direct effects. However, one also has to consider whether there is a trend in wildfires, what it is, and to what extent it can be attributed to climate change. I think there is considerable doubt about all of these issues, as discussed by Roger Pielke here. As I noted above, the IPCC has low confidence in any trend in fire weather, i.e. the weather conditions that might contribute to wild fires.
Is there a trend in wild fires? Yes, it appears to be downward since 2003.
Canada, which was recently the subject of a lot of attention about wildfires has seen a declining/flat trend since the 1990s. Claims that climate change is driving the non-existent upward trend is presented in the Guardian, New York Times, and NPR.