Four years!

WordPress reminded me that I started this blog 4 years ago today. Not really sure what to make of that. I’d like to think that I’d have some kind of insights to share, but I don’t really think I do. I’ve certainly learnt a lot, but – in some sense – I’m probably more confused than I was when I started; things I thought should be simple, clearly are not. On the other hand, some things seems clearer; we’ve had three record warm years in a row, Arctic sea ice has spent most of the last year at the lowest extent in the satellite era, atmospheric CO2 is heading towards 410ppm, and we’ve had bleaching on the Great Barrier Reef two years in a row.

I’m not really sure what else to say. Hope everyone has a good Easter break (whether you celebrate Easter, or not) and here’s a song I really like.

Posted in Personal | Tagged , , , , | 17 Comments

Emissions slowdown

I thought I would post this video of Glen Peters discussing the three years we’ve just had in which there has been near-zero growth in emissions. You can use a Kaya-like identity to try and understand what might be causing emissions to have stalled. What’s probably caused the near-zero growth in emissions is probably (in China in particular) a combination of a slowdown in GDP growth, an increase in energy efficiency (energy/GDP), and a reduction in the amount of CO2 released per unit of energy (a combination of switching from coal to gas and an increase in the use of renewables).

CO_2 = GDP \times \dfrac{energy}{GDP} \times \dfrac{CO_2}{energy}.

A key point in the talk is that these could all be signs that emissions might peak sooner than expected, but that this will require some kind policies to lock in. Also, achieving some kind of temperature target will also require emissions to actually reduce, not simpy stall. That will probably require increased deployment of renewables (which is apparently progressing about as well as can be expected) along with the deployment of some heavy-hitters, like nuclear and CCS (which are not progressing particular well). We can’t really say yet if emissions have acually peaked, but it’s at least a sign that it might happen sooner than we might have expected. Anyway, that’s all I need to say (probably more than I need to say).

Glen Peters’ post about this topic.

Posted in Global warming, IPCC, Policy | Tagged , , , , , , | 32 Comments

Toys, pram, out!

It seems that Roger Pielke Jr is having a bit of a rant on Twitter about an interview Michael Mann gave about the recent Congressional Hearings. He accuses Michael Mann of lying about him and also suggests that he might file an ethics complaint to Michael Mann’s university. I, initially, did not notice because, like many others, I’ve been blocked by Roger. If you do want to see the tweets, they’re archived here (scroll down a little). Roger’s made a bit of a habit recently of complaining about his treatment, and I have been a little sympathetic. I also thought some of what he presented at the Congressional Hearings was reasonable. However, I also think he brings much of this upon himself by being rather selective in what he presents, and by not being careful enough in how he does so.

However, the bizarre thing about this particular situation is that, if you listen to the interview (as I have), his name is not mentioned at all. The only relevant comment is at 6:56, where Michael Mann says (H/T Eli)

There are three witnesses that actually are sorta in the fringe of scientists who do not accept the science of climate change or the reality of the impacts of climate change.

The three scientists being referred to here are Judith Curry, John Christy, and Roger Pielke Jr. It seems like a pretty mild kind of comment to me. It even says sorta in the fringe, rather than definitively in the fringe. Roger may dislike that this is how he is perceived, but it’s my impression that this is indeed how many do perceive him. I don’t think he was called by the Republicans to give evidence at the hearing because he is regarded as a mainstream voice. I realise that he claims to accept the science of climate change, but if someone has to explicitly tell people what they accept, then maybe they aren’t making that clear enough when they actually discuss the topic publicly.

Ultimately, people are entitled to make judgements on the basis of what someone else says, and are entitled to express those views publicly. They also don’t need to change their mind just because the other party disputes the judgement. If Roger really dislikes being regarded as being sorta in the fringe then he should probably try harder to make it clear that he isn’t sorta in the fringe, rather than ranting about people who characterise him as being so. The irony of this whole situation is that the one person who might have a valid complaint is Michael Mann against Roger Pielke Jr, for publicly suggesting that Michael Mann has behaved unethically.

Posted in Climate change, ClimateBall, Michael Mann, Roger Pielke Jr | Tagged , , , , , , , , | 18 Comments

Research integrity

I noticed, via a tweet from Judith Curry, that the House of Commons Science and Technology Committee is holding an inquiry into Research Integrity. I also encountered this written evidence by Michael J Kelly, Emeritus Prince Philip Professor of Technology, University of Cambridge.

In my view, there are many aspects of how we undertake research that could be improved, and many of the critiques have elements of truth. However, how we conduct research can vary greatly between different disciplines, and even within disciplines. Doing applied research, where one might be trying to develop some technology, is quite different to doing more fundamental research, where the goal might be to understand some aspect of a system that is not yet fully understood. Research that relies on observations, which can often not be easily repeated, can be quite different to research that relies more on experiments, which can often be repeated many times. Research in areas with conservation laws that provide structural constancy, such as physics, can be different to that in areas without such conservation laws (such as the social sciences). Many critiques seem to assume that research is somehow homogeneous and that a problem in one area immediately applies to all areas.

For example, the written evidence by Michael J Kelly appears to be arguing that all research should be conducted like engineering. I’m sure there are many engineers who are very good researchers, but I don’t think that engineering is necessarily an examplar of how research should be conducted, and nor should we necessarily impose the same constraints, that might apply in engineering, to other disciplines. There may be some circumstances where we would expect researchers to be risk averse, and others where we should encourage risk. If the foundations of a research areas are extremely well understood, there may be well defined procedures that we would expect researchers to follow. In areas where the foundations are less well understood, we may not be able to impose strict rules as to how researchers should carry out their analysis.

Credit: ESA and the Planck collaboration

Some of what is presented in Michael Kelly’s evidence also appears to illustrate a misunderstanding of what is actually possible in other fields. For example

In cosmology, a new theory is generally not subject to such a clear and discriminatory experiment, and the claims are not testable empirically. So cosmology remains a plausible narrative of the origins of the universe, and nothing more.

Well, cosmology is simply the study of the origin and evolution of the universe, so the last sentence doesn’t even really make sense. However, the claim that the theories cannot be tested is simply wrong. The figure on the right is the Cosmic Microwave Background (CMB) power spectrum. This is the power spectrum of the tiny temperature perturbations in the microwave radiation from a time about 400000 years after the Big Bang. The data points are from observations using the Planck satellite, while the curve is the best-fit lambda-CDM model (CDM – Cold Dark Matter).

This indicates that, to explain the observations, we need some kind of cold matter that interacts only via gravity (Dark Matter), and also some kind of extra energy, known as Dark Energy. Admittedly, we have not yet directly detected Dark Matter, and do not yet know the form of Dark Energy. There are also still people working on alternatives, such as modified forms of gravity. However, the claim that we cannot test these cosmological models, is simply wrong.

Similar, the submitted evidence says

In climate science, the models struggle to faithfully represent what has happened in the last 100 years and there is no convergence theorem that says that the models are capable of predicting what will happen in the next 10-100 years. No amount of simulation is an alternative to empirical data to make a point.

Firstly, as Tom Knutson and Robert Tuleya said, if we had observations of the future, we obviously would trust them more than models, but unfortunately…..observations of the future are not available at this time. Secondly, we can’t go back in time to make extra observations of the past. We also cannot rerun our climate with slightly different initial conditions. Models provide a way of understanding how our climate responds to various changes, and provide information as to how it might change along various different future emission pathways. Models are, however, not the only source of information; there is also a lot of empirical data. Even though it is certainly true that it is important to compare simulations to empirical data, it’s also the case that data without some kind of model is also pretty useless; you can’t interpret observations without some kind of model of the system being observed.

I’d actually been tempted to not write this post as this is all getting rather tedious. However, Michael Kelly’s submitted evidence includes a discussion of the scientific literature and how it is difficult to publish a paper with a different view, and how it’s also difficult to publish a correction. Well, Michael Kelly recently published a paper on extreme events, that I discussed in this post. The paper was pretty poor and I emailed Michael Kelly to point out a very obvious error. To his credit he admitted the error (I wasn’t the only one to point it out) and claimed that he would try to publish a correction. I’ve just checked his paper on Google Scholar, and it appears to have one citation which is not a correction. I think I’ll leave it at that.

Posted in Climate change, ClimateBall, ethics, Research, Science, The philosophy of science, The scientific method | Tagged , , , , , , | 33 Comments

Why a reasonably stable climate?

Came across a nice paper today suggesting that Future climate forcing potentially without precedent in the last 420 million years, by Foster, Royer & Lunt (I say nice because I found it quite easy to understand, not because what it suggests is possible would be nice). The paper was mainly looking at why our climate (surface temperature) has been reasonably stable for a very long time (hundreds of millions of years).

The main factors that determine our climate are the amount of energy we get from the Sun (Total Solar Irradiance – TSI) and the greenhouse gas content of the atmosphere (mostly CO2). It is well known that a star like the Sun gets more luminous as it ages, with the TSI at time t, F_s^t, given by

F_s^t = \dfrac{1}{1 + \frac{2}{5} \left(1 - \frac{t}{t_o}\right)} F_s,

where t_o is the age of the Earth, and F_s is the TSI today. The change in solar forcing with time, relative to today, can then be written as

\Delta F_{Sol} = \dfrac{(F_s^t - F_s) \times (1 - A)}{4} W m^{-2},

where A is the albedo (which is assumed to be constant). Since F_s > F_s^t, \Delta F_{sol} is negative; i.e., the solar forcing is greater now than it was in the past.

However, despite the Sun actually getting more luminous, it’s thought that our climate was actually typically slightly warmer in the past than it is now; the ‘Faint Young Sun’ paradox. As this paper illustrates, the reason is probably because CO2 was higher in the past than it is now. The change in CO2 forcing is

\Delta F_{CO_2}= 5.32 \ln \left( \dfrac{C}{C_o} \right) + 0.39 \ln \left( \dfrac{C}{C_o} \right)^2,

where C is the CO2 concentration at the time of interest and C_o is the pre-industrial CO2 level.

Credit: Foster, Royer & Lunt (2017)

Okay, this is getting a little long. What the paper then did is construct a CO2 time series for the last 400 million years. The equation above can then be used to determine the change in CO2 forcing over that time interval, while the second equation in this post can be used to compute the change in solar forcing over the same time interval.

As can be seen in the figure on the right (top panel), the CO2 forcing has – on average – dropped over the last 400 million years, while the Solar forcing has increased. When combined (bottom panel), since these are the two dominant factors the control our climate, you see that the net forcing has – on average – decreased slowly over the last 400 million years. This both explains why we’ve been warmer in the past, despite the Sun being fainter, and why our climate has been reasonably stable (reductions in CO2 roughly balancing the brightening of the Sun).

Credit: Foster, Royer & Lunt (2017)

What the paper then did was to compare future changes in atmospheric CO2 and forcings with their estimates for past changes. As the top panel of the figure on the left shows, we have the potential to produce atmospheric CO2 concentrations that are comparable to, or potentially even greater than, the highest values in the last 400 million years. If we compare the combined CO2 and Solar forcing, the lower panel shows that even an emission pathway that might be quite likely (RCP6) could produce an increase in forcing that is comparable to the reduction that has occured over the last 400 million years. This would take us back to a climate similar to that during the Eocene. What is more, we have the potential to produce a change in forcing that could produce a change to our climate that is without geological precedent in the last half a billion years.

Anyway, I just found this quite an interesting paper, which gives a nice explanation for why our climate has been reasonably stable over geological timescales, why it was warmer in the past despite the “Faint Sun”, and also shows how we have the potential to make changes that could be unprecedented on geological timescales. It’s also interesting to consider why the change in CO2 forcing has almost exactly balanced the increase in Solar forcing. I guess that if this hadn’t been the case, we may not have been here to ponder this issue.

Posted in Climate change, Global warming, Greenhouse effect, Research, Science | Tagged , , , , , , , | 66 Comments

It’s okay to lie?

The House of Commons Science and Technology committee have just concluded an inquiry into science communication. One of those who presented evidence was David Whitehouse of the Global Warming Policy Foundation.

David Whitehouse’s evidence focussed mainly on science journalism, and some of what he presented was quite reasonable. It would be nice if science journalism didn’t so often involve simply copying university press releases (not all do, but it does seem quite common). Would be good if science journalists did a bit more actual investigation (although some are very good). However, the most amazing part of his evidence was his final point:

Some argue that free speech does not extend to misleading the public by making factually inaccurate statements. But it does. ………….. the freedom of speech principle does not mean that you have to be factually accurate. …… If someone says something others deem inaccurate then demand a say, not their silence. Whatever one’s stance one should criticise, highlight errors, make a counterbalancing case if it will stand up, but don’t censor, even by elimination. …..

Technically, I think he’s correct; with some exceptions, people are allowed to say things that are not true. What, of course, the above ignores is that this has little to do with freedom of speech. Our right to say certain things, does not mean that doing so is somehow acceptable. There are societal norms, which means that even if we are legally allowed to say and do things, we often choose not to. For example, we don’t typically go around saying nasty things about other people, even if they’re true. Similarly, we expect an organisation that claims to be providing information to the public, and to policy makers, to be presenting information that they at least regard as being true (i.e., they’re not being intentionally dishonest). In some cases, the latter can be required in order to maintain a certain status.

So, yes, freedom of speech may allow for people, and organisations, to mislead the public, but as a society we mostly expect that people, and organisations, do not intentionally do so. What’s maybe more interesting about the above quote is the implication that even if some are intentionally misleading the public, those who respond should aim to do so in a reasonable/responsible manner. It’s essentially suggesting that even if they behave in some socially unacceptable manner, that the response should still be socially responsible.

This is the fundamental issue, though; if you feel free to violate societal norms, then you should expect others to do the same. You can’t give yourself the freedom to do so, while expecting others to not do so (okay, you can – of course – argue for this, but it would be silly to expect it). However, this kind of thing seems rather common. Many of the complaints about the public climate science debate appear to be more about discouraging criticism than about any real desire to improve the dialogue.

Similarly here, we have an argument that people should respond responsibly in cases where another party may be intentionally misleading the public and policy makers. Well, there may be cases where a reasoned response would be the optimal way to respond. There will be others, however, where calling them liars (or whatever other descriptor may seem most suitable) may be both justified and optimal. If it’s clear that the other parties are behaving dishonestly, and are not actually even trying to present credible information, then responding as if they are may simply make their obviously disingenuous arguments seem far more credible than they actually are. The problem, of course, is that sinking to their level then makes one no better than they are, so it is a very fine balancing act.

DeSmogUK’s article.
Article in the Independent.

Posted in ClimateBall, ethics, Policy, Politics, Science | Tagged , , , , , , | 199 Comments

Hearing about climate science and the scientific method

I’ve been travelling and so haven’t really had much chance to keep up with what’s going on. I have, however, finally managed to watch the Congressional Hearing on Climate Science: Assumptions, Policy Implications and the Scientific Method. It was all rather predictable and this Washington Post article pretty much nailed it in advance.

Judith Curry played the uncertainty card and then suggested that the inability to definitively attribute periods of warming in the past, suggested that we can’t make strong attribution claims about recent warming periods. Well, this is silly, since we clearly have much more information about the recent past than we do about the distant past. The whole attribution issue has also been covered extensively, both here and on Realclimate. Ideally, Judith should recognise that just because she is uncertain about this, does not mean that everyone is uncertain.

John Christy played the lack of a hotspot card and also promoted his model-observation comparison, that he claims illustrates that the models have failed. There is an interesting Climate Dialogue discussion about the tropical hotspot, in particular the contribution by Steven Sherwood. I was pleased that, during the hearing, Michael Mann pointed out that if the troposphere has indeed warmed less than we expected, that that would imply that our climate is more sensitive than we expect, not less, since the tropical hotspot is indicative of a negative feedback. John Christy’s model-observation comparison is also discussed in this Realclimate post and it’s clear that there are a number of issues to consider, such as how you baseline the datasets, the model spread, and the structural uncertainty in the observations. It seems clear that the discrepancy between the models and the observations is nowhere near as large as his comparison suggests.

Roger Pielke Jr’s presentation was more interesting, in that I found some of what he said quite reasonable. He brought up a carbon tax, mentioned that we were unlikely to be able to substantially reduce our uncertainty prior to needing to make policy decisions, and even mentioned that, in many cases, we would not necessarily expect a trend in extreme events to have emerged, even if we would expect it to emerge were we to continue emitting CO2 into the atmosphere. On the other hand, he stills seems to blur the distinction between not detecting a trend, and there being no trend. He seems to ignore that, in many cases, we’re interested in whether or not there is an increase in the intensity and frequency of the most extreme events, rather than simply an increase in these events overall. He seems to fail to properly distinguish between detection and attribution, and he often focuses on damage/cost without making it all that clear that a lack of a trend in these does not necessarily imply anything about physical climatology.

I think this is a bit unfortunate, because these are important and interesting issues, and it would be good if he could be more careful in how he presents his information. It should be possible to do so in a way that is consistent with the evidence, allows for more meaningful discussion, and makes it harder for others to criticise what he says (which he appears to particularly dislike). On the other hand, one can’t discount that this is a feature, rather than a bug.

You’ll notice that there are two things I haven’t really mentioned. One is Mike Mann’s testimony, which was pretty much mainstream science (or, more correctly, science), and the other is how the hearing focussed somewhat on various conflicts in the public climate debate. Well, the latter just seems rather irrelevant to me, even though I do think that we should avoid attacking those who present alternative views; I’m all for an improved public dialogue about this topic, even if I don’t think it is actually possible. On the other hand, I see nothing wrong with publicly criticising what others choose to say. Even though I’m all for better dialogue, I’m certainly not in favour of not criticising what others say when it’s clear that what they’re presenting is not consistent with the best evidence available today. My rather cynical impression is that the complaints about tone is motivated more by a desire to reduce criticism of what is said, than a desire to actually improve the public dialogue.


A post by Stoat, to whom I forgot to link 😉 .

Posted in Climate change, Climate sensitivity, ClimateBall, Global warming, Judith Curry, Michael Mann, The philosophy of science, The scientific method, Uncategorized | Tagged , , , , , , , | 82 Comments