The time evolution of climate sensitivity

I wanted to just post this figure from a new paper by Philip Goodwin called On the time evolution of climate sensitivity and future warming. It uses a modified energy balance approach in which multiple climate feedbacks evolve independently over time to multiple sources of radiative forcing. As many other studies have shown, the ECS you infer depends on the timescale considered. It suggests that if you consider decadal timescales, the ECS will be biased low, and that on century timescales, the ECS has a likely (66%) range that goes from just above 2K to around 3.5K, with a best estimate of about 3K.

Credit: Goodwin (2018)

Posted in Climate sensitivity, Global warming, Research | Tagged , , , | 227 Comments

We Are Science

After a few days of presentations on (gasp!) science communication, a party was being held in Iceland. Many dignitaries, a few allocutions, among them one by a lady from the banking industry, more exactly a PR big boss from a Canadian bank. (When you hear “Canadian bank,” think serious business.) To this day one of her points stuck with me.

After thanking everyone for their enlightening talks, she said something like this. “You know what attracted me first when I entered this beautiful room? The photos on the piano. Images of people. I like to see people. People like people. It’s you that fascinates me, what you say comes after.”

A story connects characters with events, persons and deeds, agents and topics. A good science piece, to me, is one that allows me to see a scientist in action, trying to solve a mystery, sharing a passion for the object of study, showing what is done, and how. The why or the wherefore comes after.

Equations, data, code, never stand alone. If you want to sell me a theory, first tell me a story in a way I can hear an authentic voice and see the glimmer in your eyes. That last part could be a metaphor, but when “going public,” consider making it as real as possible. Image and presence matter. I’ve heard of conferences offering professional shooting sessions. Performances require preparation. Actors still need directors.

Imagine a scientist in your head. Your image may differ from the silly scientist stereotype. Or not – even scientists entertain it. We got a political problem on our hands, and we want to bring about a set of science based solutions. To paraphrase Wilfrid, the scientists’ image needs to change.


This first big step isn’t enough. In an exemplary abstract, Gabriel Lenz argues that scientific practices need to change too:

Political scientists should put aside questions about whether voters are rational or irrational, informed or uninformed, and questions about how flawed democracy is. Although they are interesting, these questions are secondary. Answering them in no way helps people—it does not help them with their violent neighborhoods, their declining incomes, their flooded homes, or their dying crops. Instead, researchers should focus on the first-order question of how to improve democratic accountability.

One radical way to improve democratic accountability and help people would be for scientists to run for office. But change can take tinier steps. Angela Potochnik recalls for instance that scientific practices are shaped not just by the need for the scientific enterprise to connect with the world, but also by the need for the scientific enterprise to connect with its human practitioners and audience. Verena Halsmayer argues that we should be following artifacts in the creation of economic theories. The following suggestion would compel theoricians to concretize their insights:

What I’m suggesting may not cohere with current academic practices. I could not care less.  Academics waste too much energy on stuff nobody reads. We’re past satisfying ourselves with communicatin’  – if what you’re saying doesn’t call for any action, why say it?

Let’s try to cut the empty talk and try to rock the world with our words. It’s OK to be angry, as long as it leads somewhere constructive. It’s OK to be stressed by our predicament. It’s OK to be an advocate too:

> [C]limate scientists who wish to engage in certain forms of advocacy have considerable latitude to do so without risking harm to their credibility, or the credibility of the scientific community.

There is only one time that matters for change – immediately, as Krishnamurti said time and time again. All one needs is to put one foot in front of the other. Collective action can’t wait until all agree on everything. Religion won’t go way and conservatism won’t disappear soon. Disagreeing should make us stronger.

Humanity is the only way out for those stuck in an echo chamber. Eric Holtaus is naming every identified victim of Porto Rico as we speak. Childish Gambino sings the happenstance of Anthropogenic Global Warming (AGW) because he can:

I have no recipe to offer. Anything goes as long as we all agree on the following. The ideals of Open Science entail sharing everything with everyone. We need to show it to people because we’re all in it together, and because it rocks the world. We need to start doing things with our words. We need to accept everyone willing to fight with us, otherwise we will suffer the consequences.

Hence why we are Science.

Posted in advocacy, Climate change, Politics, Science, Scientists | Tagged | 68 Comments

Disasters and Climate Change – part 2

Since I have a bit of free time, I thought I would expand a little on my Review of Roger Pielke Jr’s book about Disasters and Climate Change. As I mentioned in my earlier post, there were a number of things I disagree with, so thought I would expand a little on those here.

One thing that should be stressed is that what the book was mostly highlighting is that there is no indication that trends in disaster losses are due to human-caused climate change. This does not mean that we have not been able to attribute changes in some extreme events to human-caused climate change, because we have; the book is focusing on trends in disasters, not trends in the extreme events themselves.

Of course, that we may not be able to detect a trend in disaster losses that is due to human-caused climate change, does not mean that there is no such trend. However, the book argues that a signal that may exist, but which cannot be detected, is indistinguishable from a signal that does not exist. The book points out that God, aliens, and celestial teapots are also examples of things for which we have no evidence, but that we might want to believe do exist.

The problem, though, is that climate change is clearly happening and is predominantly being driven by our emission of greenhouse gases into the atmosphere. It’s already changing the conditions associated with extreme events and, in some cases, we’ve even detected a climate change related influence in some of these events. It may well be that other factors are dominating trends in disaster losses, but it would be remarkable if climate change was having no impact at all. I don’t think that this means that we should assume that human-caused climate change has contributed to some of the trend in disaster losses, but does – in my view – mean that we should be cautious of assuming that the lack of a detectable trend means that there is no trend. Even if we can’t detect something now, it seems very likely that we will in the future if we continue to dump CO2 into the atmosphere.

The other thing I was going to discuss was the argument against single event attribution. The suggestion is that this abandons the IPCC framework, which involves detecting trends over climatologically relevant timescales, and then trying to establish if anthropogenically-driven climate change was a cause of this trend. The IPCC, however, is simply an organisation that produces synthesis reports; it doesn’t – as far as I’m aware – have any mandate to specify appropriate scientific methodology. Also, single event attribution is an entirely reasonable thing to do. You consider the conditions associated with an extreme event, try to determine if these conditions could have been influenced by human-caused climate change and, hence, how this may have influenced the extreme event itself. Arguing against this is essentially arguing against doing physics. Patrick Brown has a nice post that briefly discusses this and presents an illustrative video.

As usual, this post is now too long. I wanted to finish by highlighting an earlier post in which I discuss extreme events and anthropogenic emissions and argue that formal attribution is not really all that relevant; we don’t really need to do some kind of formal attribution study to be quite confident that our emission of greenhouse gases into the atmosphere will probably influence extreme events. Understanding how it will do so, and the likely impact, clearly is important, but that’s somewhat distinct from demonstrating an anthropogenic cause.

Signal, Noise and Global Warming’s Influence on Weather – post by Patrick Brown.
Extreme events and anthropogenic emissions. – earlier post about attributing anthropogenic emissions to trends in disaster losses.
Economic losses from US hurricanes consistent with an influence from climate change – a paper by Estrada, Wouter Botzen and Tol estimat[ing] that, in 2005, US$2 to US$14 billion of the recorded annual losses could be attributable to climate change, 2 to 12% of that year’s normalized losses.

Posted in Climate change, ClimateBall, Policy, Roger Pielke Jr | Tagged , , , | 75 Comments

Disasters and Climate Change

Roger Pielke Jr emailed me an advance copy of the 2nd edition of his book on Disasters and Climate Change. Roger’s email ended with I welcome your reactions, comments, critique. Past experience makes me slightly dubious, but I will take Roger at his word.

I’ve read the book, twice in fact, and am finding it quite hard to know what to say. Even though there are a number of things that I disagree with, I think it mostly presents information that is defensible. However, what I think many will conclude from reading this book is not really consistent with our best understanding of this topic.

Since I’m still recovering from having organised a conference that ran all of last week, I’m going to try and keep this short and just make some general comments. There are some specific issues that I may discuss in a later post.

The book discusses how unpleasant and difficult the public climate change debate can be. I think it definitely can be, but I also think it’s worth reflecting on how one’s style of engagement might have influenced how one’s views were received. There is plenty of discussion on whether or not disasters [have] become costlier because of human-caused climate change. The answer is no, the data don’t support claims that the rising costs of climate disasters are due in any part to a human influence on climate. There is even an argument that we should assume that the lack of a detectable signal should be taken as the signal not existing (I don’t agree with this, but will leave this for another post).

There is also a discussion of detection and attribution, that I may discuss further in another post. The book concludes with a discussion about policy and highlights the Kaya identity (emissions are basically a function of GDP, population, how we get our energy, and how we use our energy). It also highights an iron law. GDP growth is essentially sacrosant; any climate policy that will significantly impact GDP growth will never be accepted. It also discusses how difficult it’s going to be to reduce emissions sufficiently. Interestingly, it seems to mostly argue against a carbon tax (one that would have any significant effect, at least).

As I said at the beginning, there are many things I disagree with, but I think a lot of what is presented is probably broadly correct, or at least defensible. We may not yet have demonstrated that climate change has caused disasters to become more costly, it may indeed be difficult to develop effective policy, and getting emissions to reduce sufficiently is going to be very challenging. My biggest issue with the book is that, despite it containing all the necessary caveats, I think it will be used by those who oppose climate policy to argue that there is no evidence that anthropogenically-driven climate change is having any impact on us and, if it is, doing anything ambitious about this will simply not work. If that is the message that was intended, then it’s worked.

If anything, it’s hard to really interpret the intention in any other way. The final chapter seems to explicitly argue against anything too ambitious. The problem, in my view, is that there are indications that unless we get emissions to reduce soon, the resulting climate change could be severely disruptive. I think the book mostly ignores this possibility and seems to present an argument for a policy pathway that we may well be able to achieve, but that may fail to effectively address anthropogenically-driven climate change. I don’t see this as particularly helpful. Others may, of course, disagree.


Gavin Cawley has a couple of Twitter threads about the book.

Posted in Climate change, ClimateBall, Policy, Roger Pielke Jr | Tagged , , , , | 110 Comments

The ECS is probably above 2K

I have quite a large conference starting tomorrow, so will probably be too busy to write. To keep things ticking over I thought I would post this seminar given by Andrew Dessler, discussing his recent work on constraining the Equilibrium Climate Sensitivity (ECS). I’ll note that JCH posted a comment about this yesterday, but I had already seen it.

I’ve written a couple of posts about Andrew’s recent papers, but the seminar explains it all very nicely.

The bottom line is essentially that we have strong reasons to think that the lower bound for ECS is probably above 2K, despite some recent work suggesting that it might be below 2K (i.e., we largely understand why this work gets that result and why it’s probably wrong, in the sense that the ECS is more likely to be above 2K, than below 2K). Essentially, this work suggests that the likely range (17% to 83%) for ECS is about 2.4K to 4.5K, with a median at 3.3K.

Posted in Climate change, Climate sensitivity, Research | Tagged , , | 110 Comments

Linking climate change and extreme events

There’s an article in the New Republic called the media’s failure to connext the dots on climate change. I actually came across it via a blog post by Matthew Nisbet in which he argues that [Why] The New Republic is wrong to argue for journalists to label every extreme weather event and disaster as linked to climate change. Not only do I think he slightly misrepresents what the New Republic article is suggesting, I also think what they suggest is mostly quite reasonable. I’ll try to explain why.

Climate change is clearly happening and it is mainly driven by our emission of greenhouse gases (mostly CO2) into the atmosphere. Doing so causes atmospheric CO2 to increase, reducing the outgoing energy flux and causing energy to accumulate in the climate system. This will lead to warming of the surface and troposphere, increasing ocean heat content (and increasing sea surface temperatues), an increase in evaporation, an increase in the frequency and intensity of extreme precipitation events, and a change in the latitudonal temperature gradient that has the potential to influence the jet stream and, hence, weather patterns. This means that in regions that are susceptible to extreme weather events, the conditions will increasingly tend to favour these events becoming more extreme.

I will admit that we could sometimes be more careful about how we associate climate change and extreme events, and there will almost certainly be situations in which it’s not really appropriate to include some discussion of climate change. However, climate change is clearly changing the environment in which these extreme events are occuring and, in many situations, leading to conditions that make it likely that we will see an increase in both the frequency and intensity of such events.

I think it’s important that this is understood. Even if we cannot definitively attribute a climate change link to a specific event does not mean that we can’t discuss how climate change is likely to impact such events and whether or not we’re seeing changes that are consistent with what is expected. If we want to make ourselves more resilient to such events, then it would seem important to understand how climate change is likely to influence them. Furthermore, until we get net emissions to almost zero, the climate will continue to change and we will likely continue to see an increase in the frequency and intensity of many of these extreme weather events.

To be clear, maybe I misunderstand some of what is being suggested. Also, maybe there are subtle reason why avoiding associating extreme events with climate change will somehow help us to become more resilient to these events. On the other hand, I do find it difficult to understand how avoiding discussing a climate change link will somehow help us to develop policies that effectively address this issue. Maybe I’m just a naive physicist (okay, yes I probably am) but if we do want to think about how to address the risks associated with climate change, then we really should be discussing it openly so as to help the public, and policy makers, better understand how it is likely to impact us, both now and in the future.

Posted in Climate change, ClimateBall, Environmental change, Global warming, IPCC, physicists, Policy, Severe Events | Tagged , , , | 48 Comments

You only need about 60 surface stations

Since surface temperature changes are correlated over distances of about 1000 km (it does depend somewhat on the latitude of the stations), it turns that you only need about 60 stations to produce a reasonable surface temperature dataset. [Edit: As Andrew Dessler points out in this comment, this is true for temperature anomalies, but not for absolute temperatures.]

I realise that Nick Stokes has covered this a number of times before. However, it’s probably worth repeating. Also, the main reason I wrote this is because I came across a site that allows you to experiment with this yourself. I have to admit that someone else highlighted this on Twitter, and I can’t remember who it was. If I remember (or someone reminds me) I’ll give credit [Edit: Someone has reminded me. Credit to Marcus N. Hofer]. I’m also not sure of the source of the site [Edit. It’s from Kevin Cowtan and it’s highlighted in this Skeptical Science post.].

I quickly produced the figure above. I used the GHCN adjusted plus ocean data. I initially used all the stations, then 1/10 of the stations, then 1/25, and then 1/80 (only 65 stations). The time-series look very similar (as expected). The mean trend, however, does vary slightly, but the uncertainty (not shown – see Nick Stokes’ posts for a discussion of the uncertainty) also increases. The reason, I think, that the mean trend increases slightly as the number of stations goes down, is that land stations start to dominate more and more over ocean stations, and the land is warming faster than the global average.

To be clear, I’m not suggesting that there aren’t any potential issues with the global surface temperature datasets (see one of Victor’s posts for some discussion of this). I’m mainly just trying to highlight that the sampling is almost certainly not much of an issue; you don’t need lots and lots of stations to produce a reasonable approximation for how global surface tempertures have changed. I also thought others might like to try some other variations, so wanted to highlight the site that allows you to do so (see link below).

Nice comment from Kevin Cowtan suggesting that a somewhat more careful analysis would suggest that you need maybe 130 stations. Doesn’t really change the key point; you don’t need an enormous number of stations if what you’re wanting to estimate how global surface temperatures are changing (temperature anomalies, rather than absolute temperatures). There’s a video explainer, which I’ve posted below.

Tool for producing global surface temperature datasets.
Spectral Approach to Optimal Estimation of the Global Average Temperature (Shen, North and Kim paper suggesting that you only need about 60 stations to produce a global surface temperature time series).
Global trends of measured surface air temperature (Hansen and Lebedeff paper demonstrating that surface temperatures are correlated on scales of about 1000 km).
Why raw temperatures show too little global warming (Victor Venema’s post).
Just 60 stations? (One of Nick Stokes’ original posts about only needing 60 stations).
Global 60 Stations and coverage uncertainty (Nick Stokes’ post about what happens if you cull down to 60 stations).
Are the CRU data “suspect”? An objective assessment (Realclimate post by Kevin Wood and Eric Steig demonstrating that in fact you probably only need about 30 stations).

Posted in Climate change, Global warming, Science | Tagged , , , , , , , | 43 Comments