A reduced climate sensitivity!

Now that I have your attention, I should probably make clear that this post is not about the Earth. I’m just back from a meeting where one of the speakers was Ian Boutle, lead author of a paper in which they Explor[ed] the climate of Proxima B with the Met Office Unified Model (pre-print available here).

Proxima Centauri B is a recently discovered Earth-sized planet in an 11-day orbit around Proxima Centauri, the closest star to the Sun. There are a couple of aspects of this system that may influence the planet’s climate sensitivity. One is that the star is much cooler than the Sun, and so emits most of its radiation at longer wavelengths. The other is that the planet is probably tidally locked – its rotation period will match its orbital period so that one side always faces its host star.

What Boutle et als. model indicates is that the above factors appear to result in a climate sensitivity that is quite a bit lower than that of the Earth (about two-thirds). One reason is that the albedo of ice decreases with increasing wavelength. Since the host star to Proxima Centauri B emits mainly at longer wavelengths (compared to the Sun) the ice albedo feedback is significantly reduced. Also (and this is the bit I wasn’t quite clear on) the changes in cloud cover appear to mainly occur on the night side, and so have little impact on climate sensitivity. There also appears to be global-scale circulations that also suppress the temperature on the day side, due to the efficient cooling of the night side of the planet.

The above has some potentially interesting implications for habitability. To be clear, we don’t really know what is required for a planet to be habitable, or not, so – in this context – it simply refers to the possibility of there being liquid water on the surface. However, if Proxima Centauri does have a smaller climate sensitivity than the Earth, then this implies that it is less sensitive to changes in stellar flux and, hence, that there is a greater range of parameter space over which it could support liquid water on its surface.

Of course, this is all based on models, so we don’t know even if Proxima Centauri B actually has an atmosphere and, if it does, if it can actually support liquid water on its surface. However, future space missions (such as the James Webb Space Telescope) and future ground-based telescopes (such as the European Extremely Large Telescope) might be able to make observations that could tell us something about Proxima Centauri B’s atmosphere, so we may have some idea about this in the not too distant future.

Posted in Climate sensitivity, Research, Science, The scientific method | Tagged , , , , , | 13 Comments

The feedback paradox

Realclimate has a new post, by Rasmus Benestad, that discusses predcitable and unpredictable behaviour. It focuses a little on Judith Curry’s recent report about climate models, that I discussed here. The Realclimate post is well worth reading, and I encourage you to do so, but there was one thing that I really liked and that I thought I would repeat here.

What’s quite often been discussed/mentioned here is that if one argues for a significant natural contribution to our long-term warming, then that’s potentially arguing for a high climate sensitivity. Any internally-driven long-term warming will require some kind of feedback in order for it to be sustained. However, such a physical process should respond to both internally-driven and externally-driven perturbations. Therefore arguing for a significant natural contribution to our observed warming AND arguing for a low climate sensitivity is potentially paradoxical.

I won’t say more and will simply repeat, below, the section from the Realclimate post, which explains it better than I can (credit: Realclimate/Rasmus Benestad).

A potential feedback paradox

Curry also introduces a potential paradox in her report when she emphasises natural variations. The magnitude of natural temperature variation are regulated by feedback processes and have physical causes. The climate sensitivity also involve such feedback processes.

Any feedback process based on temperature will act on both natural and forced changes in the temperature. If such feedbacks result in pronounced natural temperature variations, they also imply that the climate sensitivity is high.

Examples of such feedbacks include increased atmospheric humidity and reduced snow/ice cover. Processes involving clouds are more uncertain, but they too are likely to be affected by temperature (convection) and act to modify the climatic response.


It is possible to get enhanced variability on those timescales as a result of dynamical mechanisms without needing to appeal to higher climate sensitivity.

Nevertheless, the bottom line is that Curry must prove that the feedbacks involved in the natural variations are different to those affecting the climate sensitivity before she can conclude that natural variability dominates over a warming due to increasing greenhouse gases.

Posted in Climate sensitivity, Judith Curry, Science | Tagged , , , , | 139 Comments

Matt Ridley responds to Tim Palmer

I came across a response, by Matt Ridley, to Tim Palmer’s talk. I’ve posted Matt Ridley’s response below. One interesting aspect of his response is that it is written as if he is someone with the expertise to actually debate the science. Of course, it’s a free world, so anyone can choose to do so, and Matt Ridley does have a science PhD (DPhil actually), but his research work was in biology (which he himself points out) and he hasn’t – as far as I’m aware – been actively involved in research for over 30 years. So, his science background is not really relevant to climate, his career has mainly been in journalism, banking and politics, and yet his response does not make any of this clear. It’s not necessarily required, but I do think most would acknowledge this type of thing.

Anyway, his response is below and I’ll make some specific comments below it.

Credit: Matt Ridley

He seems to dismiss paleo estimates in a manner that does not make much sense. I don’t think the higher end of climate sensitivity, or the dependence on temperature, somehow implies runaway. Mostly, the paleo estimates are consistent with the climate sensitivity range presented by the IPCC.

  1. This point is almost saying that he agrees with Tim Palmer followed by a comment that suggests he missed the point. The outcome is, of course, not certain, but depends on a number of factors, such as climate sensitivity (which we don’t know, but we can at least produce a likely range) and how much we will emit (which we also don’t know, but can at least influence). In a sense, the more we dismiss the possibility of it being dangerous, the more we are likely to emit, and the greater the possibility of it then being dangerous.
  2. Maybe the reason Tim Palmer presented only one dataset is because all the surface datasets are very similar? Maybe the reason he chose to present GISSTemp is because it suffers from less coverage bias than HadCRUT4? Maybe the reason he didn’t show the satellite datasets is because he was talking about surface temperatures, which they don’t measure? Maybe the pause isn’t quite as big a deal as Matt Ridley would appear to think that it is?
  3. Matt Ridley is, of course, free to be unconvinced; there isn’t some requirement that he be convinced. Of course models are tuned in some respects, but this doesn’t suddenly mean that climate sensitivity is not emergent. In fact, Tim Palmer explains this all quite clearly in his talk. Also, basing his concern about models in general on possible problems with economic models, suggests he doesn’t understand the concept of structural constancy.
  4. I think he’s wrong about biology being left out of the story. As far as I’m aware, biology is considered when studying the carbon cycle.
  5. What mismatch between models and observations?
  6. As far as I’m aware, his PDF did take Nic Lewis’s work into account; the lower bound was 1.5K which – I think – was reduced from 2K mostly because of recent energy balance estimates which we should treat with some caution (to be fair, we should treat all estimates with some caution). Also, discussing these energy balance models and why we should be cautious about accepting their results was a pretty key part of Tim Palmer’s talk, so it’s odd that Matt Ridley would ask this question.
  7. I’m guessing Matt Ridley doesn’t get the irony of this comment?

It’s clear that Matt Ridley does not like Bob Ward.

Posted in Climate change, Climate sensitivity, ClimateBall, Global warming, Research, Science, The scientific method | Tagged , , , , , | 52 Comments

Informing versus convincing

I want to clarify something about yesterday’s post that seems to have at least got one person up in arms. The key point that I was trying to get across (and that I think is the same as Michael Tobis’s point) is that, formally, the role of scientists/researchers is to try and understand whatever system it is that they are studying. They also have a role in informing the public and policy makers about their research. However, they are not responsible for whether or not what they present is accepted; they’re not salespeople trying to sell a product.

However, this does not mean that they’re absolved of all responsibility. I do think that scientists/researchers should (mostly) be obliged to speak out when they’re aware that our best understanding is being misrepresented publicly. This, however, does not mean that they should be responsible if the public remains unconvinced. It’s neither their remit, nor something for which we’d expect them to typically have the necessary skills. To be clear, if some scientists do want to try and convince the public, I think that’s fine, as long as they’re honest about what they’re doing. There’s nothing wrong with scientists becoming activists as long as they make their role clear.

I think there is also a few other things to bear in mind. Many scientists who do speak out, do so in a largely personal capacity; they don’t get supported, or rewarded, for doing so. It can therefore be very difficult. It’s time consuming and – certainly in my case – can be very stressful at times. I’ve learned – the hard way mostly – what I can do without negatively impacting my family life, my job, or my health. Even then I don’t get it right all the time. I’ve spent the last few days being verbally abused on another blog because – I think – I didn’t treat someone with the kind of respect they expected. Admittedly, it was my own fault for expecting anything different.

In my view we need to recognise some of this. Some people are doing the best they can and – in my case – don’t always get it right. It is a difficult topic and I think we need to spend more time supporting those who are trying to make a positive contribution, rather than criticising them for not doing enough, or for not getting it completely right all the time. I even accept that I’ve done some of this myself, and so certainly regret some of my own interventions.

A key reason why I think it’s important to distinguish between scientists’ role in informing (it is one of their roles) and their role in convincing/persuading (it isn’t formally one of their roles) is that I fully expect us to recognise at some point in the future that we haven’t taken this issue seriously enough. I also fully expect some to blame scientists for not having done enough. I think this would be wrong and I think we should be careful of laying the groundwork for this.

Posted in ClimateBall, ethics, Global warming, Research, Science, The scientific method | Tagged , , , , , , | 74 Comments

Scientists are not salespeople!

Gavin Schmidt posted a bunch of tweets in response to a post by Scott Adams (of Dilbert fame) in which he claims to illustrate how climate scientists can persuade skeptics. If you want to read Gavin’s tweets, Greg Laden has a post as does Mark Brandon. I think Gavin’s tweets present an excellent explanation of our current understanding. However, I would like to briefly discuss a different aspect of this issue.

Scott Adams’s argument seems to be that it should be easy for scientists to present some kind of persuasive/convincing argument and that they can’t is, therefore, indicative of some kind of problem. The issue with this is that this is not what scientists/researchers should be doing. The role of a scientist/researcher is to understand whatever systems it is that they’re studying. They then present their results to colleagues and others in the field, and they should also aim to engage with the public/policymakers. However, their role is not to convince the public/policymakers, it is simply to present information. It’s for others to decide if the public should be convinced and it is the role of others to do the persuading/convincing.

What motivated this was a series of tweets by Michael Tobis which encapsulates the issues. So I’ll leave it there and you can read Michael’s tweets, which are below.

Posted in Climate change, Research, Science, The philosophy of science, The scientific method | Tagged , , , , | 51 Comments

The Ivory Tower

This is a post I’ve been thinking about for a while, and my thoughts are still not fully fleshed out, but I’ll have a go at writing it anyway. You sometimes encounter a suggestion that academics regard themselves as living in some kind of ivory tower from which they rarely emerge, and from which they can look down – disdainfully – on everyone else. I don’t, however, think this is generally true; there are clearly some arrogant academics who think they are better than everyone else, but that’s probably true for most professions. Most academics that I know are just trying to do their jobs to the best of their abilities, and typically feel quite lucky to have ended up where they have.

However, I think there is an element of truth, but not in the way most would expect. I’ve now worked in five different universities in three different countries, and although I’ve had some bad experiences, it’s mostly been very positive. You get to interact with interesting people; you get to do interesting and challenging things; you get to visit, and live in, interesting places. What also helps is that you mostly interact with people who speak the same language and have a similar background; although I should probably explain what I mean by this.

Although academia can be very culturally diverse, most will have undergone a similar training and will speak the same scientific language; they will understand the terminology and will have the relevant background knowledge. This means that you can have interesting (and often pleasant) discussion that don’t degenerate because someone misinterprets some terminology, or doesn’t understand the basics. Also, many discussions aren’t really arguments; someone isn’t trying to win – all those involved are often quite happy to just learn something from others.

However, when academics venture out into informal settings, like social media, what they encounter can be very different. They will encounter those who claim to understand a topic, but don’t. They’ll encounter those with little research experience, who claim to know how it should be undertaken. What start off as friendly discussions can turn sour when someone misunderstands some terminology, or doesn’t understand the basics. They will encounter people who think the goal is to win some kind of argument, rather than to simply have an interesting discussion. I can easily see why some might look at this and simply decide that it’s not worth venturing out.

Having said that, I have found venturing out very interesting. I’ve learned a lot about myself; I’ve learned a lot about other people; I’ve learned a lot about the public understanding of science; I’ve even learned a lot about science, and the scientific method – I’ve read things I wouldn’t otherwise have read. I think, mostly, it has been a positive experience. However, it has been very time consuming, stressful at times, and – in some cases – very unpleasant. It’s not something I would necessarily recommend, even if I think it can be a net positive experience.

As I said at the beginning, my thoughts on this are not fully formed, so I’m not entirely sure what I’m trying to get at. I guess one thing that does cross my mind is that public engagement should be about more than just discussing science, and presenting scientific results. What would be useful is if there could be a better understanding of the scientific method/process, so that maybe there can be a better understanding of why scientists/researchers engage as they do and a better understanding of the importance of terminology and what underpins some research areas. On the other hand, maybe academics also have to try and understand how they can interact publicly without running into the kind of problems that they sometimes encounter.


What partly motivated this post was this article which makes some interesting suggestions as to why science often gets shot down in the public domain.

Given the topic, it’s probably worth highlighting some of my earlier posts about ClimateballTM.

Posted in ClimateBall, Global warming, Greenhouse effect, Research, Science, The philosophy of science, The scientific method | Tagged , , | 31 Comments

Advocacy and scientific credibility

To the surprise of few, I suspect, it appears that scientists can advocate without damaging their, or the scientific community’s, credibility. It’s reported in this paper, [d]oes Engagement in Advocacy Hurt the Credibility of Scientists? and is discussed in this article.

The bottom line appears to be that there are forms of advocacy that do not negatively impact credibility, but that advocacting for something specific may do so:

Our results suggest that scientists who wish to engage in certain forms of advocacy may be able to do so without directly harming their credibility, or the credibility of the scientific community. …..Therefore, at a minimum, it is a mistake to assume that all normative statements made by scientists are detrimental to their credibility.

That said, negative effects may occur, depending on the specific policy endorsed.

I think this is somewhat similar to what I’ve always thought; how a scientist’s advocacy is received depends on whether it is something strongly supported by the scientific evidence, or something that is clearly strongly influenced by their own views/opinions. Pointing out that addressing climate change will require reducing emissions, might be a form of advocacy but it is strongly supported by the evidence and isn’t very specific (it doesn’t say how to do so, and doesn’t even rule out continuing to use fossil fuels). Advocating for something very specific, however, could influence a scientist’s credibility.

Maybe the most insightful comment was from Simon Donner (H/T Doug McNeall), quoted in this article

“public audiences are arguably more comfortable with advocacy by scientists than scientists are with advocacy by scientists,”

Yup, certainly my impression, although I would add that another group who are uncomfortable are those who don’t like the implications of what the evidence suggests.

Anyway, I think this all seems reasonably obvious to me (okay, that doesn’t mean that it’s right); I think most people would expect scientists/researchers to speak out if their research indicates that there are risks associated with various activities. The researchers just have to be a little careful about how they do so – it’s better to present information that is strongly supported by the evidence, rather than advocating for specifics that might depend on personal opinions more than on the actual evidence. Having said that, I don’t think scientists/researchers should not do the latter, they should simply be very clear that they are expressing their personal opinion, rather than expressing a view that is strongly supported by the scientific evidence.

Other posts:

Gavin Schmidt on Advocacy.

Science and Silence.

Science and Policy.

Posted in advocacy, ethics, Policy, Politics, Research, Science, The philosophy of science, The scientific method | Tagged , , , , | 55 Comments