No, it probably isn’t mostly due to changes in clouds!

I haven’t done a paper debunk for a while, but a reader got in touch to ask about a recent paper by Hans Rolf-Dübal and Fritz Vahrenholt, so I thought I would have a quick look. The paper is Radiative Energy Flux Variation from 2001–2020 and is in the open-access journal Atmosphere. The paper doesn’t actually draw any strong conclusions, but it does stress that [t]he declining TOA SW (out) is the major heating cause (+1.42 W/m2 from 2001 to 2020), where TOA stands for top-of-atmosphere, and SW is short-wavelength.

What the paper is essentially claiming is that most of the warming over the period 2001-2020 is due to a reduction in cloud albedo which then leads to more absorbed solar radiation. This has then been used by some to claim that [c]hange in clouds likely cause of warming in the past 20 years.

I haven’t worked through the details in the paper to really know if the results they present are correct, but I don’t think the results presented in the paper are necessarily all that surprising. I think it is mostly related to what I was highlighting in this post.

There can sometimes be a rather simplistic idea about how global warming actually happens. The simple view is that adding greenhouse gases to the atmosphere reduces the outgoing longwavelength flux, producing a planetary energy imbalance, which then causes the system to warm until it returns to energy balance. What actually happens is – unsurprisingly – a little more complicated.

It is correct that adding greenhouse gases to the atmosphere does reduce the outgoing longwavelength flux and does produce a planetary energy imbalance. However, as pointed out in this paper, as the system warms, there are then feedback responses that can further enhance the reduction in outgoing longwavelength radiation (water vapour). However, there are also other responses that can counter-act this (clouds), and others (also clouds) that can lead to a reduction in albedo and, consequently, an increase in the amount of absorbed solar radiation.

As this paper then illustrates, when energy accumulates in the climate system due to an enhancement in atmospheric greenhouse gas concentrations, this accumulation is primarily due to an increase in absorbed solar radiation, rather than simply being due to an imbalance in the long-wavelength fluxes. However, this doesn’t somehow contradict that adding greenhouse gases to the atmosphere will cause the system to warm, or suggest that changes in clouds are causing most of the warming.

So, although I haven’t work through the Dübal and Vahrenholt paper in detail, the basic result they present seems broadly consistent with what is expected. That they find that most of the warming over the 2001-2020 period was due to a reduction in cloud albedo doesn’t really contradict our understanding of greenhouse warming and doesn’t suggest that most of the warming over this period was due to changes in clouds.

Most of the warming is almost certainly due to the human emission of greenhouse gases into the atmosphere. How clouds then respond to the subsequent warming then leads to most of the accumulated energy being due to an increase in absorbed solar radiation. If anything, as highlighted in the video in this post, this might actually be suggesting that equilibrium climate sensitivity is well above 2oC, rather than highlighting some major challenge to our understanding of greenhouse warming.


Outgoing longwave radiation – post I wrote explaining why most of the accumulated energy is due to increased absorded solar radiation.
Global warming due to increasing absorbed solar radiation – paper by Trenberth and Fasullo.
Shortwave and longwave radiative contributions to global warming under increasing CO2 – paper by Donohue et al.

Posted in Climate change, Climate sensitivity, Global warming, Greenhouse effect | Tagged , , , , , | 25 Comments

Riders on the Storm

I’ve just finished reading Alistair McIntosh’s new book Riders On the Storm; the climate crisis and the survival of being. I should admit that I got somewhat distracted after reading the first few chapters, so it took me a while to finish the whole book. However, I did find it a very interesting and enjoyed reading it.

I should probably admit a slight bias. It turns out that Alistair grew up in the same village on the Isle of Lewis where some of my family came from, and went to the same high school as my mother (although, somewhat later than my mother). The book uses examples of life in these rural communities to discuss how communities might respond to crises like climate change. The book also mentions the Iolaire tragedy, which I mentioned in this post.

What I did find particularly good, and which I suspect many regulars here will appreciate, is that it did an impressive job of discussing the scientific evidence, stressing that the best evidence is that presented by the IPCC. The book is also critical of both climate denial and doomism, suggesting that Climate change denial is a waste of time. But climate change alarmism is a theft of time. However, it managed to criticise climate alarmism in a way that didn’t undermine the seriousness of climate change, which – in my view – is often an issue with many such criticisms.

I also thought that the book presented what might be a somewhat non-mainstream perspective, but did so in a way that kept the discussion grounded in the realities of the problems that we face. It was neither overly optimistic, nor unduly pessimistic. In some sense it maybe didn’t provide any concrete solutions, but it did provide some thoughtful perspectives about the importance of communities and what can be achieved if people work together for the common good.

I’m probably not doing justice to the book in this brief post, but if you do want a better flavour of the book, you can read Alistair’s Realclimate guest post. I certainly thought it was a book that many of the regulars here would appreciate, so I certainly recommend reading it if you get a chance.


Rider on the Storm – Link to Alistair’s book.
Kenneth Smith – post about Kenneth Smith who died in the Iolaire tragedy.
Denial and Alarmism in the Near-Term Extinction and Collapse Debate – Alistair’s Realclimate Guest post.

Posted in Uncategorized | 49 Comments

The Hack That Changed the World

After airing the movie, The Trick, the BBC has also broadcast a series of podcasts on Climategate called the Hack That Changed the World (H/T Dikran Marsupial). I’m not sure if all can listen to them, but I thought they were pretty good.

Apart from “skeptics”, and a few scholars who still choose to write about Climategate, most seem to now accept that the emails were hacked, have been cherry-picked and taken out of context, and may well have played a role in delaying effective climate action. What’s not known is who actually carried out the hack, and even though that was a focus of these podcasts, it’s still completely unclear.

What might be of most interest to regular commenters here is the final episode, which focuses on the skeptics who were involved in trawling through the emails. It focuses partly on Steven Mosher, who has been a regular commenter here and has published a couple of guest posts.

Although most here may already know this, the podcast highlighted that after Climategate Steven worked with Berkeley Earth and pretty much confirmed that there were no major problems with the global temperature datasets. Steven also acknowledged that he learned that you need to be more than a data analyst to understand complex issues; you do also need some expertise in the relevant field.

Towards the end of the final podcast, Steven was asked what he would say to Tim Osborn and Phil Jones today, and he basically said that he would apologise, mostly for the way in which he characterised them at the time. Given how Climategate impacted some of those involved, I suspect some would still not accept this. However, since people rarely seem willing to acknowledge their errors, this seemed worth highlighting. It would be nice if people could be more charitable all the time, but being willing to acknowledge, and apologise for, a lack of charity is maybe a reasonable step.

Posted in Anthony Watts, Climate change, ClimateBall, Global warming, Steven McIntyre | Tagged , , , , | 110 Comments

The concept of net-zero

I’ve written about this before, but thought I might discuss it again. There seems to be a recurring narrative that the concept of net-zero is flawed. It might first have been presented in this article suggesting that the concept of net-zero is a dangerous trap. I agree with much of what is presented in the article. Net-zero plans tend to rely on technologies that have not been shown to work at a suitable scale, or rely on technologies that will almost certainly not work as intended. Additionally, a consequence of relying on these technologies is that there has been little in the way of actual emission reductions. It’s likely that this will continue as new net-zero plans are developed that will probably also rely on carbon removal technologies, rather than on actual emission reductions. However, none of this explains why the concept of net-zero is flawed.

The basics is all very simple. Global warming is happening, it is pre-dominantly due to the human emission of greenhouse gases, mostly carbon dioxide, and will continue while carbon dioxide continues to be emitted into the atmosphere. Consequently, stopping global warming requires that human-caused carbon dioxide emissions go to zero. This could happen through simply stopping emissions, or through removing and storing as much carbon dioxide as is emitted into the atmosphere. Hence, net-zero.

That many plans for reaching net-zero may not actually achieve this goal and may be being used to delay making actual emission reductions doesn’t mean that the concept is flawed. Why not criticise the net-zero plans, which may well be dis-ingenuous, rather than claiming that the concept is flawed? Claims that the concept of net-zero is flawed makes it sound like we shouldn’t be aiming for net-zero which, given the current net-zero plans, may well be where we are currently heading.

What I don’t get is why those who create this narrative don’t do so in a way that makes clear that they’re criticising they way in which the concept is being used, rather than the concept itself. As Gavin Schmidt points out in this debate with Benny Peiser, the basics that underpin net-zero are pretty simple and very well understood.

Posted in Climate change, Global warming, Scientists | Tagged , , | 91 Comments

It’s not too late

In the run up to COP26, the University of Edinburgh has had a series of conversations with researchers about how to make the world a better place through our actions, activities, innovation, research, teaching and learning. I agreed to be involved in one about why it’s not too late. It was hosted by Susan Morrison, and also included Elizabeth Bomberg, a political scientist, and Richard Milne, a plant biologist.

All the conversations were posted live to youtube, and you can find the series here, and our conversation here. We also producedk a few short videos that were shown during the conversation. I produced a short one about that tried to explain why it isn’t too late. I’ve posted a lin to it below, but bear in mind that I was trying to explain climate change, net zero, carbon budgets, feedbacks, runaway, and tipping points, in less than 4 minutes.

Posted in Climate change, Global warming, Research, Uncategorized | Tagged , , , , | 19 Comments

Systemic misuse of criticism of climate science

I thought that those familiar with the climate debate might be interested in the latest saga. About a year ago, Roger Pielke Jr and Justin Ritchie wrote a paper called Systemic Misuse of Scenarios in Climate Research and Assessment, which I briefly discussed in this post. They also promoted this in Issues in Science and Technology, in an article called How Climate Scenarios Lost Touch With Reality.

Yesterday, Issues published some responses to the claims made by Pielke and Ritchie. The authors include Marcia McNutt (current President of the National Academy of Sciences), Chris Field (co-chair of the IPCC’s Working Group II), Kate Marvel (climate scientist at NASS GISS and Columbia), Gavin Schmidt (Director of NASA GISS and Senior Climate Science Advisor to the NASA Administrator) and Peter Jacobs (Strategic Science Advisor, Earth Communications, NASA GSFC).

I think the resonses are very good, although I don’t entirely agree with McNutt and Field that it is still 100% accurate to regard RCP8.5 as a business-as-usual pathway. I think most now agree that this is not a good descriptor for this pathway and that maybe we should avoid using this desriptor altogether.

I did particularly like the ending of the response by Schmidt & Jacobs

Thus, assessing the worth of scientific contributions by counting which scenarios are mentioned is like assessing honesty by counting the number of times the word integrity is used in an article; it is both pointless and misleading.

The response on Twitter from Roger Pielke Jr was rather predictable. He complained that some of the responses were lying about their work. Some of the responses suggested that Pielke and Ritchie were claiming that the “use” of these scenarios was a failure of scientific integrity, when what they were really suggesting was that the “misuse” was a failure of scientific integrity. Of course, they also suggest that there is systemic “misuse” of scenarios, so it’s not entirely clear when their “use” isn’t “misuse”.

Roger also suggested that the reason climate scientists are mad with him is because he’s spent many years writing about the conflicts between the special interests of the climate science community and the broader social responsibilities of this community, rather than because he’s spent decades criticising climate scientists in ways that have provided ammunition for those who either dispute AGW, or its significance.

Climate science is a complex science and there are certainly valid criticisms that could be made about the development of scenarios, the modelling choices, and how some of this work has been presented publicly, to name but a few. However, I suspect that measured, constructive criticism will produce far fewer headlines than claims that there has been systemic misuse of scenarios, and that this is a failure of scientific integrity. It also won’t appeal nearly as much to those who dispute that dealing with climate change requires urgent action, but far be it for me to suggest that this might have been a motivation behind the Pielke and Ritchie critique.

For those who are familiar with the climate debate will realise that this is just another example of same ol’ same ol’. As Gavin Schmidt pointed out on Twitter, it’s not as if Roger doesn’t have form.


Systemic Misuse of Scenarios in Climate Research and Assessment — Article by Pielke & Ritchie.
How Climate Scenarios Lost Touch with Reality — Issues article by Pielke & Ritchie.
Climate Scenarios and Reality — Response from McNutt & Field, Marvel, and Schmidt & Jacobs
Poor Roger — post I wrote about some of Roger’s contributions to the climate debate.

Posted in Uncategorized | 23 Comments


I’ve written a number of posts about methane and have also described an updated global warming potential metric, typically called GWP*. I happen to quite like this updated metric, but I noticed a tweet suggesting that it was

*designed* to benefit high-emitting countries and industries.

I found this suggestion a little odd, and posted a tweet thread of my own. However, since I have a blog, I thought I could turn it into a blog post too 🙂

A few years ago I was somewhat cofused about why there was so much focus on methane. If it has a relatively short atmospheric lifetime (~12 years) then it shouldn’t accumulate in the same way as CO2 and should have a different impact on long-term warming.

I tried asking people about this, but couldn’t really resolve my confusion. I even engaged in an email exchange with colleagues at my university, but they didn’t seem to understand what I was asking and just repeated the standard GWP values.

I then came across work by Michelle Cain, which described a new metric called GWP*. This new metric seemed to do a much better job of representing the warming due to a short-lived greenhouse gas like methane than the more standard GWP100, or GWP20, metrics. If you want to understand this new metric, this Carbon Brief article is very good.

As someone who had been confused about the focus on methane, this new metric seemed to be an obvious update that largely resolved a flaw with the standard GWP100, or GWP20, metrics (which don’t really distingush between stock and flow pollutants). It seemed much more likely that this work was motivated by trying to solve this issue, than it being *designed* to benefit high-emitting countries and industries.

However, it is the case that some could use this new metric to claim that they were no longer contributing to global warming because, for example, they were no longer increasing their methane emissions. Also, methane is responsible for quite a lot of warming (~0.5oC if you include the direct and indirect effects). If methane emissions are not reduced, then this warming will persist and this will make it extremely difficult to meet some of the targets.

However, from my perspective, if we want to use metrics to estimate the impact of different greenhouse gases, then it seems preferable to use ones that do a reasonable job of this, than to stick with ones that have flaws, even if such an update may be misused by some to argue against reducing their emissions.

Also, I can’t really see any reason why GWP* couldn’t be used to demonstrate how different industries/countries have contributed to historical warming, how they might contribute to future warming, and how future emission cuts could be apportioned. The standard GWP metrics might be easier, but that doesn’t necessarily imply better.


Posts I’ve written about methane.
Posts I’ve written about GWP*
Guest post: A new way to assess ‘global warming potential’ of short-lived pollutants — Carbon Brief article about the new GWP* metric.
Improved calculation of warming-equivalent emissions for short-lived climate pollutants — Michelle Cain et al’s paper about GWP*.

Posted in Uncategorized | 47 Comments

Science communication

I listened to one of Andy Revkin’s Twitter broadcasts with Randy Olson which discussed if science communication was worse now than it was 100 years ago. I’ve actually read most of Randy Olson’s book, where he introduces his 3-step model for science communication.

I found the discussion quite interesting, and I think he makes some good points about the importance of narrative. The argument seems to be that there is a huge problem with misinformation and that scientists missed a great opportunity, in the past, to engage with those who had expertise is creating appealing narratives.

His prime example was Michael Crichton, a very successful author and filmmaker, who had a scientific background. He acknowledged that Crichton later started promoting science denial, which he suggested was partly a response to being ignored by the scientific community. What he doesn’t seem to consider is that this is a classic example of the power of motivated reasoning and illustrates why it is so challenging to effectively communicate contentious scientific topics.

My issue with this whole kind of narrative is the idea that if only scientists had done something different, we wouldn’t be in this current mess. I have no doubt that there are many things that scientists could have done better, but that’s true for almost anything. What I’m yet to be convinced of is that there was some relatively simple thing that could have been done that would have substantively changed where we are today. I don’t really think that there was.

It’s not even clear that scholars in relevant disciplines even agree about what misinformation is being spread and who is doing it. There are prominent, and well-regarded, scholars in some disciplines who are regarded, in other disciplines, as associating positively with those who promote misinformation and potentially even spreading it themselves. How are we meant to counter this when there is this kind of disconnect between disciplines?

I highlighted this disconnect on Twitter and was basically told by another scholar that I was in a Twitter echo chamber and that most of the vocal people in my circle are not engaged with or trusted by governments (which was a bit odd, given who I would regard this as including). Even if this was a valid criticism, it still seems to highlight the problem with trying to counter misinformation.

To be clear, I don’t really have some simple solution to this conundrum. I think effectively countering misinformation is very challenging, and I do agree that scientists who engage publically could learn from those with expertise in creating appealing narratives. I don’t, though, think that there is some simple way for scientists to engage that would somehow solve this problem, especially given that it seems that those who try, can end up in conflict with scholars from other relevant disciplines.

Posted in Pseudoscience, Science, Scientists | Tagged , , , , | 48 Comments

Science-based targets

It may just be my bubble, but I seem to be encountering quite a lot of criticism of things like deadlines, net zero and carbon budgets from people who – as far as I can tell – support aggressive climate action. I have to admit to not fully understanding the arguments being made, but I think it has to do with these science-based targets not really telling us how to meet these goals. The idea, I think, is that we should be focussing on the socio-political (or socio-economic) barriers that have really been hampering efforts to address these environmental problems.

I certainly agree with the basic idea that science-based targets don’t tell us how to achieve these goals. I also largely agree that there are many barriers to making effective progress. What I haven’t understood, despite asking a number of times, is how focussing more on dealing with these socio-political, or socio-economic, barriers avoids turning this into ideological battle that potentially also undermines the ability to deal with climate change, and other environmental problems.

A reasonably common claim in the climate debate is that many who profess to be concerned about climate change are really just using this as a way of promoting their preferred socio-political ideologies. So, if we move away from highlighting science-based targets, to focus more on the socio-political barriers to action, how do we do so in a way that doesn’t lead some to simply say “told you so“?

Similarly, if we focus more on these socio-political barriers, this would seem to also run the risk of validating Lomborg-like arguments that suggests that the main way to deal with climate change is simply to make everyone richer and, hence, more resilient. In other words, if dealing with socio-economic inequality is seen as a key step to addressing climate change, why are Lomborg-like arguments not entirely valid options?

As I said, I may well misunderstand the criticisms of these science-based targets, and I may not have expressed my concerns as clearly as I could have. However, I do think that one advantage of the science-based targets is that they’re under-pinned by pretty robust evidence. If we largely dismiss these science-based targets, and we focus instead on dealing with the socio-economic barriers that are seen to be hampering action, how do you distinguish between solutions that have the potential to also deal with climate change, and other environmental problems, and those that do not?

Posted in Climate change, Global warming, Policy | Tagged | 66 Comments

Estimates of the economic damages from climate change

Since I’ve discussed climate economics before, I thought I would briefly highlight a recent seminar involving, amongst others, Steve Keen and Tim Lenton. The topic was are the estimates of economic damages from climate change erroneous? The basic answer to this questions is yes.

The presenters make a number of good points. Steve Keen highlights how there is little empirical support for the damage functions. There are attempts to estimate how economic activity depends on climate, but there is a huge difference how it might vary in different regions of the planet today, and how it might be impacted by global warming of a similar magnitude.

Tim Lenton highlighted how we may already be close to triggering certain tipping elements and how these economic analyses tend to ignore such outcomes, or may even not be able to properly consider them. In one economic analysis, it was suggested that the collapse of the Atlantic Meridional Overturning Circulation (AMOC) may have a positive economic impact because it might slightly dampen global warming. As Tim Lenton pointed out, this was an “insane” result given that such a collapse would result a major reorganisation of the entire climate system.

Matheus Grasselli, another of the speakers, presented quite a detailed analysis of William Nordhaus’s DICE model. He highlighted how it essentially assumes that the system is always in equilibrium, even if there has been some major shock. He also showed how the results depended strongly on assumptions about damages. What I thought was particularly interesting is that in the DICE model, everything seems to recover even in extreme scenarios.

So, it seems that there is a general view that there are many valid criticisms of these economic analyses. However, at the risk of being accussed of being deferential again, I do think there are many economists who acknowledge this and who are trying to do more appropriate analyses. I do think that some of the damage estimates are way too low, and that the results of some of these analyses have been presented in ways that then play into the hands of those who want to minimise the impact of climate change.

However, this is clearly a very complicated problem and we do need some kind of idea of the economic impact of climate change and what we might be able to do to limit the impact. The key thing, in my view, is to be upfront about the assumptions used in the models, the limitations of the models, and to recognise that there are many things that to which we simply can’t assign a quantitative value. I would be interested in what others think, though.


NAEC seminar : Are the estimates of economic damages from climate change erroneous? – seminar involving, amongst others, Steve Keen and Tim Lenton.

Posted in Uncategorized | 47 Comments