The 2 degree threshold

I’ve never really written about the 2 degree threshold before, largely because I don’t really have particularly strong views about it. Scientifically, it’s a little odd to try and characterise what is clearly a very complex system with a single number. A single number can’t really tell us much about other fatcors (like ocean acidification) that are also relevant. My personal, clearly naive, ideal is that we should be able to discuss the complexities of something like climate change in more detail and shouldn’t need to focus on a single number.

On the other hand, I can see that from a policy perspective it’s beneficial to have some kind of target, so that we can then focus our policy goals on achieving that target. Even that has its drawbacks though. Some argue that the 2 degree threshold isn’t really a dividing line between safe and dangerous. This is probably true, but – in my opinion – rather irrelevant. I suspect most would agree that there is some level of warming that would probably be catastrophic. I don’t know precisely what it would be, but somewhere between 4 and 5 degrees is probably a reasonable estimate. Given that we don’t want to get close to this, a target of staying below (or close to) 2 degrees seems reasonable.

There are others who argue that even 2 degrees is too high and that we should be doing all we can to keep the warming at an absolute minimum. I have quite a lot of sympathy with this view. The problem I have, though, is that the evidence suggests that there’s little we can do now to avoid reaching 2 degrees. It’s possible that we can still do so, but quite likely that we’ll not achieve this. Arguing that we should be staying well below 2 degrees when the best we can do is – maybe – to not miss it by too much, seems a little counter-productive.

At the end of the day, I don’t have particularly strong views. I certainly see climate change as presenting risks that we should be doing our utmost to avoid. Done properly this would achieve the goal of preventing the temperature rise from reaching levels where it becomes more likely that climate change has extreme consequences. Of course, I realise that realistic policy probably requires some kind of target and so I have no issue with the 2 degree limit, I just don’t have any particularly strong reason to defend it or attack it. One reason I thought I would write this was as a prompt to get others to express their views through the comments. As usual, I might learn something.

For other views, there are a couple of interesting RealClimate posts. In the latter post, I tried to engage in a discussion with Roger Pielke Sr about determining the radiative imbalance using ocean heat content data (he hasn’t responded yet). Unless I misunderstand him, he appears to not understand the difference between an average rate of change and an instantaneous rate of change.

I thought I’d end this post with a video of Marc Hudson interviewing Kevin Anderson. Kevin Anderson makes, in my view, a number of very valid points.

Posted in Climate change, Climate sensitivity, Global warming, Science | Tagged , , , , , , | 176 Comments

2 degrees by 2036

Michael Mann and Lawrence Torcello have an article in the Conversation about the philosophy and science of limiting global warming to 2oC. This caused some controversy on Twitter because it wasn’t clear if the article referred to the Northern Hemisphere only, or to the whole globe. It also cause some controversy because 2036 seems very soon for us to reach the 2 degree limit (self-imposed limit, at least).

However, if – as the article assumes – the ECS is 3 degrees and we follow a high-emission pathway (RCP8.5) then I think 2 degrees by 2036 is plausible. An ECS of 3 degrees suggests that feedbacks amplify the warming by a factor of about 2.7 (3/1.1). This tells us that the feedbacks must be about 2.2Wm-2K-1. If we follow a high emission pathway then we will increase anthropogenic forcings by about 2Wm-2 by 2036. Given that we have a planetary energy imbalance of around 0.6Wm-2 today, if we did not warm at all, we’d have a planetary energy imbalance of 2.6Wm-2 in 2036.

To reach 2 degrees by 2036, we’d need to warm by 1.1 degrees from today (1.1 + 0.9) which would produce a negative feedback of 3.7Wm-2, and positive feedbacks of 2.4Wm-2 (2.2 x 1.1). This would then leave a planetary energy imbalance of 1.3 Wm-2 (2.6 + 2.4 – 3.7) which may actually be a little high, but not implausible. So, 1.1 degrees from today seems entirely possible, especially as we might expect it unlikely that the planetary energy imbalance could grow much larger than around 1Wm-2.

This also seems broadly consistent with a post by Ed Hawkins which seems to suggest that 2 degrees by around 2040 is plausible if we follow an RCP8.5 emission pathway. So, I’m not sure I quite get what the fuss is all about. If the ECS is indeed 3 degrees (which is close to the expected value) then reaching 2 degrees by 2036 is indeed quite possible, if we choose to follow a high emission pathway. Of course, if we do reach 2 degrees by 2036, this will not be where warming stops, since we’d still warm by about another degree or so, so as to reach equilibrium. Of course, I’m not suggesting that the exact date would be 2036, simply that reaching 2 degrees by that time is quite possible if we continue along a high emission pathway. I guess we’ll know soon enough if this is indeed possible or not; at which point we can all collectively say “shit, Michael Mann was right!”.

Posted in Climate change, Climate sensitivity, Global warming, Michael Mann, Science | Tagged , , , , , | 59 Comments

Same ol’ same ol’

Richard Tol first came to my attention when he publicly criticised the consensus project. For reasons quite hard to understand, he tried very, very, very, hard to get his commentary published, eventually succeeding.

At the same time, it became quite clear that there were a number of errors in one of Richard’s papers on the economic effects of climate change. Richard Tol submitted a correction to his paper, suggesting that it was Gremlins wot made him do it. The significance of this was discussed by Andrew Gelman (who suggested that maybe Richard Tol should try harder) and by Grant McDermott. It now appears that the IPCC has changed the wording in one of its recent reports as a result of these errors/corrections.

If, however, you read Richard Tol’s response to this, it appears that his critics are all wrong and that it is all some kind of left-wing conspiracy. At this point I’m probably supposed to make some comment about Richard’s behaviour, but I really can’t be bothered. As Joshua would say, it’s just the same ol’ same ol’. It would probably be nice if people engaged constructively with their critics, but I guess there’s no rules to say that you have to and – I guess – if you don’t trust your critics then I suspect that you won’t feel that any engagement would be of benefit.

I’ll also note that Judith Curry has responded in a similar fashion to those critical of her Wall Street Journal Op-Ed. So, all-in-all, just another couple of episodes in the never-ending game of ClimateBallTM.

Posted in Climate change, IPCC, Judith Curry, Satire | Tagged , , , , , , , , | 123 Comments

Methane and things

Given that the whole Royal Society Twitter saga relates partly to the possibility of an abrupt methane release, I thought I might post this video that I found on Climate Denial Crock of the Week (I hope Peter Sinclair doesn’t mind me using it). It’s Richard Alley explaining that our current understanding is that although there is a lot of methane on the sea floor, it is very unlikely to be released abruptly. It may well provide a feedback, but a methane “bomb” is unlikely.

This got me thinking a little about these low-probability, high-risk events. Of course, we should study and try to understand these processes, but I can see why they shouldn’t play a big role in the policy debate. We’re unlikely to drastically change our economy because of something very unlikely, even if it does present a high-risk (although how we as a society react to unlikely events does suggest that we don’t always behave in this way). We also have plenty of reason to act without focusing on such possibilities.

There is, however, a role that they can play and that some may not recognise. Richard Alley brings this up at the end of the video, which is why I thought I might mention it. There are various ways in which we can estimate how our climate will evolve under increasing anthropogenic forcings, and we can produce some kind of best estimate for the likely outcome. However, it’s not exact and we know that it could be “better” than this, and it could be “worse”. So, in some sense, there’s a symmetry – an approximately equal chance of these being “better” or “worse” than our best estimate (assuming it’s the median).

However, when it comes to the unexpected outcomes/events, this symmetry – I think – breaks. The chance that something unexpected could make things “better” is extremely unlikely. It would almost need to be fine tuned. It is much more likely that unexpected outcomes will makes things worse. So, although I can see why focusing on these unexpected events may not makes sense from a policy perspective, I do think that we can’t ignore that – if they do occur – they will likely make things worse. They also, probably, depend on the amount and rate of future warming, and so add an extra reason why we should really be seriously considering avoiding the higher emission pathways.

Anyway, that’s my view, for what it’s worth. Watch the video; Richard Alley is an extremely skilled science communicator.

Posted in Climate change, Climate sensitivity, Global warming, Science | Tagged , , , , | 30 Comments

An apology

It seems that the tweeting saga at the Royal Society meeting on Arctic sea ice continues. I wasn’t going to write about this, partly because it all seemed so childish that it was best ignored and partly because you could always read views, expressed, by others. However, my noted lack of self-restraint means I can only hold out for so long.

It all started when Prof. Peter Wadhams formally complained about those who tweeted during his talk, saying

I was subjected to unprofessional on-line behaviour of two of the co-organizers: Dr. Mark Brandon (Open University) and Dr.
Sheldon Bacon (National Oceanography Centre) and by one of the participants, Dr Gavin Schmidt, who is Director of the Goddard Institute for Space Studies.

thereby starting a process that has mainly served to indicate that Peter Wadhams has little understanding of what defines professional behaviour.

Mark Brandon, Sheldon Bacon and Gavin Schmidt have responded with a lengthy document, that also includes Peter Wadhams’s initial complaint letters (which went to the Royal Society, the Open University, NASA, University College London, and the University of Southampton).

You might imagine that it all might stop there, with everyone thinking it best to simply let the matter drop. Well, you’d be wrong. Peter Wadhams has doubled down with a new (in fact, this may be letter number 3) letter of complaint, now requesting

i) a meeting with the Royal Society and BBS [Brandon, Bacon, Schmidt] to discuss this matter in person, and
ii) a public apology by BBS and a public statement by the Royal Society on this issue.

I don’t know about everyone else, but it’s my view that unless the person requesting an apology is your partner, your parent, or your boss, an appropriate response to such a request would be piss off, you’re not getting one. On a serious note, what does Peter Wadhams plan to do if he doesn’t get his way? Keep going until people simply give in and apologise, just to get him to shut up? Actually try and damage people’s careers over a few tweets that may have been a little sarcastic (you can read them and make up your own mind), but that were mostly really informative and a fair reflection of his talk?

I have read most of the tweets and actually followed the meeting on Twitter. It was extremely useful and interesting and Mark Brandon – in particular – put a great deal of effort into tweeting relevant comments about the various talks. Peter Wadhams will be doing noone any favours if his actions discourage such activities. It’s clearly my view that he deserves no apology and that his behaviour has been unfortunate at best. On the other hand, Mark, Sheldon and Gavin may disagree and – given how difficult it can be to craft a suitable apology – I thought I might provide a template. I should make it clear that I’m not suggesting that anything said in this template is relevant in this particular case; it’s just an example of how someone might construct a suitable apology. (Given that Peter Wadhams appears to have no sense of humour, it might be best if those involved were not to tweet this post – I’d hate to make things worse).


Posted in Comedy, Satire | Tagged , , , , , , , | 22 Comments

Environmental bullies

I was wondering what others thought of Owen Paterson’s lecture to the GWPF. I read it and thought it wasn’t as bad as I was expecting (which shouldn’t really be interpreted as “good”). Some of what was said about energy was reasonable, although ignoring climate change when discussing shale gas is always a bit of a red flag. The Committee on Climate Change has, though, produced quite a strong response to Owen Paterson’s lecture.

He did, however, briefly mention his views on climate science

…let me say a few words about climate science….

I readily accept the main points of the greenhouse theory. Other things being equal, carbon dioxide emissions will produce some warming. The question always has been: how much? On that there is considerable uncertainty.

Okay, kind of alright and there is uncertainty, but this uncertainty really just means that there is a range of possible warming for each possible future emission pathway. We can use these ranges when considering the various policy options. It doesn’t mean “wait until we’re more certain”.

indeed the failure of the atmosphere to warm at all over the past 18 years – according to some sources.

This is interesting because it appears as if he’s trying to make this sound correct by adding “according to some sources”. The reality is that most of the sources indicate that we have warmed over the past 18 years. Cherry-picking a source that suggests otherwise is not particularly credible.

Many policymakers have still to catch up with the facts.


The stopping of the Gulf Stream, the worsening of hurricanes, the retreat of Antarctic sea ice, the increase of malaria, the claim by UNEP that we would see 50m climate refugees before now – these were all predictions that proved wrong.

Is this true? I’m not aware of these being credible predictions. This seems rather like a strawman argument.

For example the Aldabra Banded Snail which one of the Royal Society’s journals pronounced extinct in 2007 has recently reappeared, yet the editors are still refusing to retract the original paper.

Firstly, you don’t retract a paper simply because it’s wrong and, secondly, this paper has had far more attention in the last few months, now that some have noticed it is wrong, than it had had in the preceding 6 or 7 years. It’s much more a poster-child for those “skeptical” of mainstream climate science, than it ever was for those who are not.

I actually found his conclusions more interesting (annoying) than most of the rest of his lecture. He says

To summarise, we must challenge the current groupthink and be prepared to stand up to the bullies in the environmental movement and their subsidy-hungry allies.

Really? Bullies in the environmental movement? Also, we might disagree about whether or not there is groupthink and – if there is – who is suffering from it. This also just seems a bit whiny and pathetic for an ex-government minister. Also, people who tell you that you are wrong aren’t necessarily bullies. He goes on to say

Paradoxically, I am saying that we may achieve almost as much in the way of emissions reduction, perhaps even more if innovation goes well, using these four technologies or others, and do so much more cheaply, but only if we drop the 2050 target, which is currently being used to drive subsidies towards impractical and expensive technologies.

I always find this type of suggestion quite frustrating. It’s kind of saying that we can achieve what is wanted, but only if we do it the way he wants to do (he’s not alone in presenting this type of argument). Possibly, I guess, but if it’s possible to achieve the required emissions reductions, then why is there such disagreement? If it is possible to do so, why are we not simply working together to achieve these goals? Of course, some would argue that it’s only possible if we do it in a particular way, as every other way is simply too inefficient or will never work. If so, then this is fundamentally an ideological argument. The interesting thing, though, is that it does seem to be an acknowledgement that it is possible to achieve emission reductions without destroying the economy, so a step in the right direction – maybe?

Posted in Climate change, Global warming, Science | Tagged , , , , , , | 256 Comments

Being positive!

I’ve been doing what I do quite a lot these days, which is contemplating the whole online climate science debate. It’s very clear that any kind of dialogue with those who strongly disagree with mainstream climate science is virtually impossible. I know that some British climate scientists are trying, but either they don’t read contrarian blogs or, if they do, they do so with blinkers on or are much more forgiving than most.

Given this, I’ve been wondering about what is the best way to engage. One could be dismissive and rude about contrarians and impugn their character, but that just means turning into Anthony Watts and I’m certainly not willing to go that route. One could mock the contrarian views, but there are others who are more capable of that than I am. My current thoughts are that it would be good to be able to present a more positive picture, but I’m having some trouble seeing how that is actually possible.

One way to appear positive is to adopt the lukewarmer position, which is essentially that climate sensitivity will be low and that everything will be fine. The problem with this is that although it could end up being correct, it might not. Additionally, the evidence actually suggests that this is more likely to be wrong than right. It’s one thing to be optimistic and positive, but doing so by ignoring swathes of evidence that suggests that you’ll probably be wrong seems naive.

An alternative is what I think is the Pielke/Lomborg/Breakthrough Institute position. This seems to be that the priority is to simply continue to grow our economies and become wealthier and wealthier. If we do so, we’ll eventually have sufficient wealth to solve whatever problems we might face. There are – in my opinion – numerous problems with this strategy. My personal problems with this is partly that it seems to be relying on us magically finding a solution without ever actually trying to do so, and partly that it largely ignores the inertia in the climate system. Our emissions today don’t warm us immediately, but warm us over the coming decades. Therefore if we wait until it becomes obvious that we need to find solutions, we’re largely guaranteeing that things will continue to worsen over future decades.

Given that we’re an intelligent species that has the ability to understand what the future might hold, it seems rather odd to ignore that avoiding certain outcomes requires, ideally, acting sooner, rather than later. An additional issue I have with the Pielke/Lomborg/Breakthrough Institute type message is that it seems to be accompanied by claims that nothing we do will ever work. If we get more energy efficient, people will just use more. All climate treaties have achieved nothing, therefore they’ll never work. It’s hard to see how a message that nothing we do will ever actually work is particularly positive.

My preferred position is that we are in fact an innovative, intelligent, adaptable species that has the ability to make sensible decisions so as to avoid unnecessary risks. We have all this scientific evidence that tells us something of what might happen if we continue to increase our emissions. We have various possible alternative energy sources. We have all this information that we can use to make, ideally, sensible decisions about how best to proceed. My issue is that we appear to not be doing this. If anything, we seem to be doing the opposite. Our emissions seem to be following the high emission pathway and various governments have either reduced their commitment to address climate change, or are considering doing so.

So, does anyone have any better ideas? Is there a way to present a positive message that is both consistent with the scientific evidence and potentially effective, or are we simply in a position where that isn’t really possible? I certainly don’t know the answer. I’d certainly much prefer to be presenting things positively, than negatively, but I’m rather failing to see how this is possible without either sticking my head in the sand, or becoming a rampant libertarian, neither of which I’m really willing to do.

Posted in Climate change, Climate sensitivity, Global warming, IPCC, Personal, Science | Tagged , , , , , , | 154 Comments