Probably Good has a new section on climate change

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. 

1. [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. 
2. 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). 
   1. 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. 
   2. 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. 
3. Drought 
   1. 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. 
   2. 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. 
   3. Water scarcity is mainly driven by mispricing of water and especially subsidies of water for farmers. 
4. Temperature-related deaths
   1. 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. 
   2. 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. 
5. Tipping points 
   1. 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). 
   2. 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. 
   3. 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. 
6. Conflict 
   1. 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. 

Dylan_Balfour @ 2023-11-29T18:59 (+18)

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.

Dylan_Balfour @ 2023-12-05T09:11 (+17)

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:

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.

John G. Halstead @ 2023-12-05T13:57 (+3)

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.

Thanks a lot for the response! I was the main researcher for these articles - here are a few thoughts from me and the team:

It’s a little tricky for us to evaluate the consensus on these issues ourselves as we don’t have the capacity or expertise to review all the relevant papers and assess their relative influence. (We’d welcome anyone sharing their views on this, especially if they have expertise in the field!)

Because of this, we typically defer to respected authorities – especially the IPCC – which is likely a decent proxy for expert consensus. While any one institution will inevitably have its shortcomings, the IPCC's comprehensiveness in reviewing the literature is impressive, and they do a fairly good job of representing their uncertainty based on the literature in their reports.

That being said, there seems to be a lot of uncertainty about expected adaptation efforts, perhaps more so than there is uncertainty about the direct effects of climate change, and the extent to which the IPCC provides estimates accounting for adaptation depends on the problem. In short – we don’t really know, (though we’re open to being corrected on this). 

Because of this, when trying to estimate the value of working on adaptation, given high uncertainty about how much of it will take place without our intervention, as well as a reportedly widening adaptation finance gap, it’s still worth thinking about the expected impacts assuming minimal or current-trajectory adaptation. Though, naturally, the more we learn about the impact of expected adaptation efforts, the better.

Here’s a few more specific points on deaths from non-optimal temperatures and natural disasters:

On temperature and mortality:

When discussing the promisingness of an adaptation response to heat stress, we think what matters is the absolute numbers of heat-stress-related deaths, which we can be quite confident will significantly increase, and not whether on net climate will cause or prevent more deaths (taking into account other types of deaths prevented). We included the estimate that increases in fatalities will outweigh reduction in deaths because it provides interesting and relevant context, not because it directly bears on how promising this area of adaptation is.

It’s also worth noting that even Zhao (2021) claims that ‘in the long run, climate change is expected to increase the [temperature-related] mortality burden’, even if it reduces mortality in the short term. They don’t give any concrete projections, so it’s unclear the extent to which the numbers we’ve given align with this claim – but the direction is the same. Nonetheless, this does complicate the discussion around temperature-related mortality, so thanks for bringing it to our attention!

On natural disasters:

First, although fatalities from natural disasters have decreased, most of this reduction has been in high-income countries (if you look at the OWID page and filter by low-income countries, the downward trend is much less clear). 

Additionally, looking at the decadal average of all natural disasters can hide how sparse the data points driving this impression are. If we look at the year-by-year view of natural disaster deaths, just a handful of terrible events are responsible for the vast majority of deaths throughout the 20th century, which means we’re wary about inferring long-term trends from the decadal view – especially for events that fit a power-law distribution.

On top of this, looking at the specific kinds of natural disasters we’re discussing, it’s not clear they’re subject to the same downward trend, even on the decadal view. For instance, the OWID chart on natural disasters shows deaths from extreme temperatures have sharply increased in recent decades, and annual flood deaths have been fairly flat since the 1970s.

And just as a general point on the importance of climate-related extreme weather events, only counting fatalities may also give us a misleading picture, since it excludes other significant effects like damage to infrastructure, worsened mental health, and cumulatively huge economic losses. Again referring to the OWID page, the economic damage inflicted by natural disasters is much higher now than it was in the 1960s (as a share of GDP), despite them causing fewer deaths.

Our current view is that looking at the century-long average as an estimate of expected future fatalities may be an overestimate (primarily due to reductions in high-income countries), but it’s unclear that existing adaptation efforts will similarly continue to reduce harms going forward (or prevent potential rises in disasters where such are expected due to climate change).

The bottom line is we think there’s a lot of complexities in the analysis of the quantitative estimates, especially when adaptation and human response is a critical factor. But we believe that the areas we’ve identified are nonetheless promising areas to have a positive impact given what we know. 

John G. Halstead @ 2023-11-30T14:53 (+14)

the economic damage inflicted by natural disasters is much higher now than it was in the 1960s (as a share of GDP)

You cannot infer trends in the climate-related economic impact of natural disasters from trends in the total damage of natural disasters or trends in the per capita economic impact of natural disasters. The economic costs of natural disasters is influenced by the increasing economic value of areas that are vulnerable to climate change.  Eg here is a Miami beach a century ago compared to today

You need to adjust for this by producing an estimate of normalised damages (discussed here by one of the most cited climate researchers). For example, here is the normalised cost to the US of hurricanes since 1900. i.e. suggestive of increased losses on the order of $5-10bn over the course of a century, which is about 0.2% of US GDP. 

Despite what you read in the media, according to the IPCC, for the vast majority of extreme events, it is not yet possible to attribute with confidence any change to climate change. A white entry in the table means that a signal cannot yet be noticed with confidence. A blue entry means the signal is increasing. An orange entry means the signal is decreasing.

There is as yet no clear evidence of a climate signal for precipitation, flooding, drought, fire weather, wind speed, storms, cyclones, and coastal flooding.

John G. Halstead @ 2023-11-30T13:02 (+6)

I don't agree with your points on natural disasters. I am going to post below the charts from OWID on weather-related deaths, including absolute numbers and per capita numbers. Some comments:

• These numbers are (now thankfully) small, falling well well short of catastrophe. 
• There have been massive declines in the absolute and per person risk from the most threatenting risks (droughts, floods). This is due to economic development. 
• To characterise the trend in flood deaths as anything other than a dramatic downward trend seems clearly wrong. 
• For all the media discussion of wildfires and a world on fire, we have passed 1 degree and wildfire deaths are 140 per year, which is far exceeded by the number of people who die falling off ladders. Perhaps not today, but at some point the media and the scientific community are going to face scrutiny for exaggerating on climate change. 
• Extreme temperature deaths are increasing, but this would (I assume) include cold-related deaths and heat-related deaths. According to Zhao et al, cold-related deaths are 9x heat-related deaths today, so one would expect the 1C we have already experienced to have reduced the death toll. In the absence of climate change, the increase would be more pronounced. (I haven't looked into the data source though)
• There is large net migration (i.e. in the millions of people) to low lying coastal areas in Asia that are most vulnerable to coastal storms. This, rather than climate change significantly confounds trends in per capita or total storm deaths. Nevertheless, storm deaths are at historic lows for any ten or twenty year period in the 20th Century. 
• As indicated by your comment, if your concern is reducing deaths from climate change, the main thing to do seems to be to increase economic growth in poor countries given that is what drove the massive decline in weather-related deaths over the last 200 years. 

Dylan_Balfour @ 2023-12-05T09:14 (+11)

I again genuinely appreciate this feedback, and what I said above also applies here: we’ll revisit the content with your comments in mind and will likely make some changes. Because I’ve already given some object-level discussion in this thread, I wanted to provide a response to this claim: 

For all the media discussion of wildfires and a world on fire, we have passed 1 degree and wildfire deaths are 140 per year, which is far exceeded by the number of people who die falling off ladders. Perhaps not today, but at some point the media and the scientific community are going to face scrutiny for exaggerating on climate change. 

Whilst you’re correct that direct deaths from wildfires are low, these are not what primarily drive deaths caused by wildfires; the indirect effects from wildfires (via air pollution) are much larger. 

For instance, Ye, et al (2022) attributes over 130,000 deaths to wildfire-related PM2.5 exposure in Brazil from 2000-2016 (>8,000 per year), and Chen et al (2021) seemingly attributes around 30,000 deaths per year from 2000-2016 to wildfire-caused pollution, globally. 

It is difficult for me to verify every assumption in these papers, but even if they’re significant overestimates, it’s clear that indirect deaths from wildfires vastly outnumber direct deaths. Several other papers that directionally support this point (with a fairly wide range between estimates):

Kollanus et al (2016): >1,000 deaths in Europe in both 2005 and 2008 

Neumann et al (2021): 720 deaths per year in Western US, 1996-2005

Pan et al (2023): 4,000 deaths per year in US, 2012-2014

Johnston et.al (2015): 339,000 global deaths per year, 1997-2006 (from landscape fires - a broader category than wildfires)

Roberts & Wooster (2021): 677,745 global deaths per year, 2016-2019 (also from landscape fires)

Of course, the extent to which climate change drives wildfires, both now and into the future as warming increases, is an important crux in how many of these deaths we should attribute to climate change. But, when evaluating the importance of wildfires themselves (e.g. when thinking about adaptation), looking just at the direct harms will lead us to significantly underestimate their impact. 

John G. Halstead @ 2023-12-05T13:31 (+2)

Yes, those are good points 

Vasco Grilo @ 2023-11-28T15:58 (+4)

Thanks for the detailed reply, Dylan!