Myles Allen explains it all at RealClimate

Myles Allen first hit the headlines when a research project that he was involved with issued a press release (26^th Jan 2005) predicting that temperatures could rise by 11° C even if the amount of CO₂ in the atmosphere is limited to only double the level before the Industrial Revolution. Given that temperatures only 6°C higher than today are considered to be catastrophic, this warning received extensive and highly sensationalised coverage in the media. But all was not quite as it appeared to be.

There is a transcript of part of a BBC Radio4 programme made by Simon Cox and Richard Vadon some time later called Overselling Climate Change, see here. This gives a brief but fascinating account of the controversy that followed. It is essential reading for anyone who wishes to follow the rest of this post.

On 21st April 2006, soon after this programme was broadcast, even RealClimate.net, the most strident advocates for anthropogenic global warming on the net, put up a post entitled How not to write a press release criticising Myles Allen’s handling of the affair. This carried some authority, as the proprietors of this blog are all leading figures in climate research. Normally in this field, dog does not eat dog, but in this case the way in which climateprediction.net had publicised their research seemed to be so unacceptable that general condemnation was called for.

All this might now have passed into history as other apocalyptic predictions claimed the limelight. Two recent posts on the internet have brought the issues raised at that time back into focus.

At climateaudit.org, Steve McIntyre announced that, more than a year after the IPCC began to publish its 4th Assessment Report, they had finally been persuaded to make public all the information about how the review editors on the project had carried out their duties. His observations were not encouraging for those who would like to think that the IPCC assessment process can be relied on.

The review editor’s function is a very important one in a process where vast amounts of scientific research is being reviewed: some more robust, some less so, some supporting the orthodox view, some challenging it. No one would describe it as an easy job and the vast egos that scientists can exhibit when their research, and professional reputations, are at stake make it no easier. In a sense, the review editors are the umpires of the IPCC assessment process, charged with ensuring that everyone gets a fair hearing, that researchers are able to ensure that their work has not been misunderstood or misrepresented, and most important of all, where there are areas of genuine and irreconcilable disagreements, ensuring that this is made clear in the report. This (in part) is how the IPCC describe the duties of a review editor.

Review Editors will assist the Working Group/Task Force Bureaux in identifying reviewers for the expert review process, ensure that all substantive expert and government review comments are afforded appropriate consideration, advise lead authors on how to handle contentious/controversial issues and ensure genuine controversies are reflected adequately in the text of the Report.

Although responsibility for the final text remains with the Lead Authors, Review Editors will need to ensure that where significant differences of opinion on scientific issues remain, such differences are described in an annex to the Report.

Steve McIntyre’s post can be found here. It makes fascinating reading.

Among the Review Editors who can be identified from links at the climteaudit.org post is Myles Allen, who was appointed to discharge this duty on Chapter 10, Global Climate Predictions. In PR terms, this was arguably the most important part of the report, because it is forecasts about the future of the climate above all that have aroused the concern of policy makers and the general public about global warming.
The second post that I want to refer to was one at realclimate.org entitled Blogs and peer-review. The thrust of this has little to do with what follows here, but the comments that it attracted about the climate prediction.net press release do. They include contributions from Myles Allen, Richard Vadon who produced the Overselling Climate Change programme for the BBC, plus Gavin Schmidt and Stephan Rahmstorf both proprietors of the realclimate.org blog. The latter two are also vocal, prominent and very effective advocates in the cause of anthropogenic global warming. Schmidt is closely associated with climate modelling at NASA and Rahmstorf was a lead author on the palaeoclimate chapter of the 4th Assessment Report. Both are very big hitters indeed, but by contrast there is also a single sentence comment that I submitted, not realising quite what dramatic consequences such a minor contribution to the discussion would have. Here are the comments:

5 · Myles Allen Says:
3 April 2008 at 5:55 PM

Dear Gavin,

You may feel you didn’t criticize the Stainforth et al paper, but you did misunderstand it in one crucial respect, in that you said explicitly that our “the most important result … is that by far most of the models had climate sensitivities between 2ºC and 4ºC, giving additional support to the widely accepted range.” I didn’t think it mattered at the time, but it turned out it definitely did matter, because this was the first thing those BBC journalists threw at me, and I continue to meet journalists and even scientists who are convinced that your analysis was in fact our “true” result, and we only drew attention to the fat tail extending out to much higher sensitivities because we wanted to alarm people. As you know (and noted in your later post, thanks), the cluster around 3 degrees wasn’t a result at all, but a simple artifact of the experimental design, so the fat tail was indeed the main noteworthy result of the experiment.

It would have been really easy to have picked up on this had you e-mailed me a draft of your post before posting it on the internet (and published our response along with your post if necessary). It’s all water under the bridge now, but this whole exchange does demonstrate the serious collateral damage that can be caused by relatively minor mistakes. Now that RealClimate has proved such a success and is so heavily used by journalists for source material, perhaps it is time to tighten up your procedures a little. I personally would never comment critically in public on a peer-reviewed paper even to point out “obvious problems” (who is the judge of what is obvious here?) without at least exchanging e-mails with the authors to make sure I had understood it correctly (I’m more than happy to criticize non-peer-reviewed material on Channel 4).

While I’m posting (I can see how you guys get into this) I’m also very uncomfortable with your notion of “tacit knowledge:” it certainly seems to be tacit knowledge in the blogosphere that the chances of the climate sensitivity (equilibrium warming on indefinite stabilization at 560ppm CO2, for the non-enthusiasts) being greater than or equal to 6 degrees are too small to be worth worrying about (meaning down at the level of an asteroid strike). If we accept this tacit knowledge, then your original post and the fuss over the press coverage of Stainforth et al make a lot more sense: we would have had no business drawing attention to these high-sensitivity models if we were as confident as you all seem to be that the real world sensitivity just cannot be that high. But (although of course I sincerely hope you’re all right) I just don’t see the evidence for this level of certainty in the peer-reviewed literature. In an environment without peer-review, it seems to me to be much easier for such “everyone knows X” myths to develop.

I appreciate that publish-first-and-ask-questions-later is “traditional” practice in blogging, but perhaps, as scientists, we should be challenging that practice. After all, if the New York Times can pass articles through a simple fact-check procedure before publishing them, why can’t RealClimate?

[Response: Dear Myles, thanks for your thoughts. I was only able to join this discussion late, so you find my response down at comment #116. -stefan]

19 · Richard Vadon Says:
4 April 2008 at 6:28 AM

I produced the Radio 4 programme you described as “rather scurrilous”. Unsuprisingly I think this is unfair and I am very proud of the programme. I invite people to make their own minds up. The programme is what climate change journalism should be it is challenging and rigourous. It does not feature any sceptics to falsely balance the debate and allows people we criticise to defend themselves.

The page below has the programme available in full in the top right-hand corner.

http://news.bbc.co.uk/1/hi/magazine/4923504.stm

Many scientists have contacted me privately to commend the programme but I will mention a couple of people close to CPDN [Climate Prediction Dot Net] who have written about the programme and the press release.

Tim Palmer, the head of the Probability and Seasonal Forecasting Division at the European Centre for Medium-Range Weather Forecasts wrote the following in Physics World:

” A recent well-researched BBC radio programme exposed a number of exaggerated press releases by climate institutes.”

Bryan Lawrence of NERC [Natural Environment Research Council] who fund CPDN said on his blog of the infamous press release:

“I was staggered to read the actual press release that caused all the fuss (predictions of 11C climate sensitivity etc). The bottom line is that had I read that press release without any prior knowledge I too might have believed that an 11 degree increase in global mean temperature was what they had predicted (which is not what they said in the paper). I can’t help putting some of the blame back on the ClimatePrediction.net team – the press release didn’t reflect the message of their results at all properly, and they shouldn’t have let that happen. I’m still naive enough to believe it’s incumbent on us as scientists to at least make sure the release is accurate, even if we can’t affect the resulting reporting.”

I can imagine that this is exactly the kind of blog comment that needs stopping.

In the original programme we also touch on frogs and the huge amounts of coverage giving to the frogs killed by climate change story. The brilliant Andrew Revkin wrote about this recently:

http://dotearth.blogs.nytimes.com/2008/03/24/vanishing-frogs-climate-and-the-front-page/

It looks like we were right in our approach to the story. It was a story I couldn’t have hoped to have covered without blogs. They helped me realise there was a story but only when I had spoken to many peer reviewed scientists did we broadcast.

[Response: I have edited out the term ‘scurrilous’, since that was perhaps a little strong. However the implication that the CPDN scientists were trying to deliberately mislead the public is unfounded. That implication, nor the accusation that they were being alarmist, did not arise from our original blog posting. – gavin]

[Response: Please also note Myles’ response below. – gavin]

50 · Myles Allen Says:
5 April 2008 at 3:33 AM

Dear Richard (post 19),

I can understand that you made your programme with the right intentions, given that you felt the climateprediction.net team was a bunch of dishonest scaremongers from the outset (why else would you have taken such pains to disguise from us what the programme was actually about when you originally approached us for interview?).

And you could have been forgiven for getting that impression from what was available on the internet. Of course, Gavin and Stefan didn’t suggest we were dishonest, but if they were right that our most important result was the 2-4 degree cluster, then it would certainly have been dishonest not to have made sure that this cluster was mentioned in any press releases. But, to reiterate, that wasn’t a result at all: the study itself didn’t tell us anything about the likelihood or otherwise of the traditional range.

Since I am not aware that you actually interviewed any of the journalists who originally covered the story or who were present at the original press conference (please correct me if I’m wrong here), I can see how your views must have evolved. It is a very nice illustration of the dangers of getting too much information from cyberspace: internet discussions have their own momentum (“tacit knowledge”) that may not reflect what has actually gone on in the real world.

As I said in the discussion of your programme on RealClimate, we asked Fiona Fox of the Royal Institution to follow up with those who had actually covered the story. She kindly wrote to a all the journalists she had on record who were at the press conference asking them for their reaction to your accusations, stating:

========
…
My own clear memory of this briefing is that the scientists were very clear that the results showed a range of warming between 2 degrees and 11 degrees and that each time they were asked about the impact of 11 degrees they reminded journalists that this was the worst case scenario and it could just as easily be at the lower end. Obviously we all knew (the press officers that is) that you would report 11 degrees and the fact that this was twice the level suggested by previous studies was clearly a significant news story. However I believe that the scientists themselves were very measured and did not emphasise the 11 degrees.
…

Fiona Fox , Director
Science Media Centre
The Royal Institution
========

The responses Fiona received were as follows:
========
Hi Fiona,

My memory tallies with yours. They presented the range, they described the concept of the ensemble, they emphasised (in response to a very perceptive question from some star BBC journalist) the role of clouds in the uncertainty, they mentioned 6 main reasons for uncertainty.

If anyone went for the exaggeration it was the journalists – we all mentioned 11 degrees I’m sure but as far as I recall, PA and Metro presented it virtually as a fait accompli.

Richard Black, BBC
========
Thanks Fiona, my memory is as yours. Let me know what feedback you get and I’ll write you something properly tomorrow.

Ruth Francis, Nature
========
Hi Fiona,

As I recall, the researchers, and Myles Allen in particular, emphasised the fact that the bottom end of the range (ie the 2 in 2-11 degrees C) corresponded to previous predictions of 2-5 degrees C. I seem to remember that they said this gave strength to the prediction that there would be a warming of *at least* 2 degrees C, but that there was a greater degree of uncertainty at the top-end. This last point was definitely underlined. To back that up, refer to Myles’ quote in my article:
http://www.scidev.net/News/index.cfm?fuseaction=readNews&itemid=1878&language=1.
Hope this helps.
Catherine.
Catherine Brahic
Senior correspondent
Science and Development Network (SciDev.Net)
========
I’d agree with Catherine’s interpretation – as far as I recall, they were all quite careful to stress the greater temperature change the greater the degree of uncertainty. I’ll try and dig up the bulletins report.

Sarah Mukherjee, BBC
========
Hi Fiona – my memory is that the scientists took pains to point out that it was a range and quite a broad range at that. I also remember Myles in a rather vivid phrase saying that we had to remember that we could still take actions to avert the worst warming and that we shouldn’t assume “that our children will stand by and watch as the seas boil around them”, showing that the worst case wasn’t necessarily the most likely outcome.
Thanks,

Fiona Harvey
Environment Correspondent
Financial Times
========

I am not aware of anyone who covered the paper who did not either attend the press conference, speak to a project team member, or use an agency report from someone who had done (again, if your research revealed otherwise, please correct me). The Natural Environment Research Council Press Office assured me that all recipients of their press release (including all those quoted above) would have received it attached to the paper and would have known that it was intended simply to draw attention to some interesting results in the paper, not to provide a comprehensive summary. Judging from the responses above, it appears they were absolutely right.

[Other readers may like to know that all this information was available to Richard before the airing of his programme: since Richard is still encouraging you to go and listen to it, you might like to ask yourselves how balanced it really is in the light of the above responses from the people who were actually there.]

Tim Palmer and Bryan Lawrence would not have known about this context (nor, indeed, would any of the scientists you interviewed for your programme), since despite the fact that your programme was about coverage of a scientific story, you apparently didn’t want to talk to anyone who had actually covered it.

Gavin is probably right that scurrilous was a bit strong, since I accept your intentions were in the right place. Misguided would have been a better word.

Regards,

Myles Allen

Gavin: is there any way this response could be pushed up next to Richard’s? I’ve made these points before, but as far as I can tell no one noticed because they were too far down the thread (another example of the fallacy of the “you can always correct mistakes by responding on the blog” argument).

51 · Hank Roberts Says:
5 April 2008 at 7:04 AM

Have the people who actually wrote the original press release spoken up in this thread or elsewhere? I mean by that the people who put the words together in the form sent out, probably by a marketing or PR department staffer. Their job is getting the organization’s name into the news, not writing abstracts with real info.

53 · Myles Allen Says:
5 April 2008 at 8:13 AM

In response to Hank (51):

I think the offending paragraph was written by a long-suffering Natural Environment Research Council press officer who has since moved on to other things. But I don’t think it’s fair to tee off on the press officers, who have a pretty thankless task. If I recall correctly the 11 degree number went in and out of successive drafts like a yoyo, and ended up being left in on the grounds that it had to highlight something “new and concrete” – not, I might add, “alarming”: my impression was that the Press Officer would have just as happily drawn attention to zero-sensitivity models, if we’d have found any.

Anyway, I eventually signed it off on the understanding that no serious mass-circulation journalist would rely on the press release in reporting the story, and that its sole purpose was to encourage journalists to find out more. It seems, judging from the responses Fiona got and despite Richard Vadon’s claims, that this understanding was correct.

The press release could undoubtedly have been clearer, but it seems no-one who reported the story directly actually misunderstood what had been done, so it didn’t in fact do any damage. But of course, if Richard had stuck to “scientists issue a press release that might have been misunderstood but wasn’t” his editors probably wouldn’t have been very impressed.

Of course, if Richard can come up with journalists who did report the story solely on the basis of the press release and did not understand that 11 degrees was the top end of a large range, then that is a different matter. So far, no one has come forward to my knowledge.

61 · Myles Allen Says:
5 April 2008 at 2:11 PM

Dear Hank,

I know it’s almost as fashionable to knock journalists as it is to knock press officers, but to be honest, I was very reassured by the results of Fiona Fox’s inquiry (which, after Richard’s initial allegations, I was rather dreading). The journalists not only clearly understood the story perfectly well (in spite of, you might say, the unclear wording of the press release), they could remember all about it in remarkable detail more than a year on (Fiona Harvey of the FT could even quote me verbatim).

In many ways the worst libel in Richard’s piece was the claim (which has since been repeated by other BBC journalists) that his colleagues were just copying out the press release, when he knew perfectly well they were doing nothing of the kind.

Myles

64 · Richard Vadon Says:
5 April 2008 at 3:36 PM

Hi Myles

I can’t believe we are doing this again. Let’s stop soon

As you know my position is that you judge the journalists on what they write. The broadsheet articles on your story did not give the readers a proper understanding of your research. We quote them in the programme. They make it sound like the world was about to end. Let’s be clear that this is first and foremost the responsibility of the journalists and headline writers involved. I know that you at CPDN were appalled at some of the coverage. The question we asked in the programme was, did the press release play a part in this?

I think you are correct when you say “The press release could undoubtedly have been clearer”. In our programme you didn’t say that. I think if the press release had been clearer the coverage wouldn’t have been so apocalyptic. I know you disagree. I suggest people listen to our interview with you. You put your view strongly and clearly.

The programme is available here :

http://news.bbc.co.uk/1/hi/magazine/4923504.stm

66 · Myles Allen Says:
5 April 2008 at 3:58 PM

Dear Richard,

The journalists who covered the story clearly understood it, so while the press release might have been mis-understandable (what press release isn’t?), we made sure no-one actually misunderstood. What the headline writers (who wouldn’t have even read the press release) chose to say was beyond our (and, I understand, even the journalists’) control.

Did you interview anyone who actually covered the story who you were accusing of acting highly unprofessionally in just copying out the press release? If so, why did you not include that in the final version of the programme? I think you (and Bryan Lawrence, Tim Palmer and all) would have got a very different impression of what happened if you had done.

I appreciate by the time you got the results of Fiona Fox’s inquiry the BBC had already invested too much in the programme to change it, but I don’t see why you are defending it now.

Myles

68 · Myles Allen Says:
5 April 2008 at 5:54 PM

Response to 67: It was the huge range, 2-11 degrees, and the asymmetry relative to the traditional 2-4 degree range, that we felt was the important result, not the fact that the “vast majority of their results showed that doubling CO2 would lead to a temperature rise of about 3C”, as Richard Vadon put it in the web version of his programme (this cluster was simply an artifact of the way we had imposed the perturbations). It was also important that it wasn’t just a “tiny percentage” showing high values, as Richard claims, but a systematically fat-tailed distribution (20% higher than 7 degrees, if I recall correctly).

I think our interpretation of the Stainforth et al results was correct. Certainly, the paper has been cited quite a few times (including by the IPCC, with appropriate caveats, of course) as evidence that climate sensitivity could be a lot higher than the traditional range. No one, to my knowledge, has ever cited that study as providing support to the 3 degree traditional value. To this extent, it seems that the journalists Richard Vadon was criticizing appear to have understood the significance of the study rather better than he did. It’s a shame he doesn’t appear to have talked to any of them.

Myles

• TonyN Says:
  6 April 2008 at 9:48 AM

Re: 50 Myles Allen

It was very thoughtful of Fiona Fox to provide the journalist who attended the press conference with her own recollections of what had happened more than a year previously when asking for theirs.

81 · Myles Allen Says:
6 April 2008 at 12:29 PM

Tony,

Yes, if we’d known this was turning into some kind of forensic examination, it would have been better for her not to have written the e-mail like that (which is why I included it along with the responses). But all she knew was that a concern had been raised: we had no idea Richard Vadon was going to go to such lengths to pin the blame for the headlines on us.

Anyway, the only relevant point here is that Richard Vadon clearly thought (and presumably still thinks, since he hasn’t revised the web post on their programme) that the percentage of models we found with different sensitivities somehow told us anything about the real world. It didn’t (because of the way parameters were sampled etc. etc.), and no scientist has ever suggested otherwise in the peer-reviewed literature. The only relevant finding was the fact that the high-sensitivity models were not significantly less realistic than the normal-sensitivity models, together with the fact that there were enough of them to rule out a pure fluke (20% greater than 7 degrees is hardly a tiny percentage). He was starting out from a blogosphere myth, and working out a way to stop such myths promulgating in the first place is what this debate should actually be about.

Myles

[Response: Myles, It is not a ‘blogosphere myth’ that the most likely value for the climate sensitivity is around 3 deg C – you, me and the IPCC all agree with that. The CPDN results did not change that (and haven’t in subsequent papers either). You are conflating a minor technical misinterpretation of the histogram of CPDN results with a much bigger issue of where the CPDN results fall in the wider context. Most of the erroneous headlines were based on an interpretation of the Stainforth paper as implying that sensitivities greater than 7 (and up to 11 deg C) were now much more likely and that the predictions of climate change in the next 50 to one hundred years needed to be dramatically revised upwards. That is not the case since, as you state above, the histogram of CPDN results tells us nothing about the real world. What Vadon and Cox saw was based on this much more obvious disconnect, not one line in our original post (which after all came after all the headlines). I fundamentally disagree that the problem was our post or some ill-defined ‘myth’ that you imply we are propagating. The problem was one of insufficient context. The solution is what you found at the press conference – if the time is taken to explain things properly and make sure that people understand, then you get a better outcome (most of the time). Our efforts are therefore better directed at continually trying to improve the background context that journalists have, and not trying to find convenient scapegoats in the ‘blogosphere’.

As I stated in the post above, your NG piece did end on an interesting point, but continually dragging this conversation back to an inappropriate single example is diluting it – because we end up arguing about the specific and not the general. We will probably need to agree to differ on how influential our post was compared to the headlines in multiple mass-media outlets, but I don’t think I am alone in thinking your fire is aimed at the wrong target. – gavin]

86 · Myles Allen Says:
6 April 2008 at 5:30 PM

Hi Gavin,

Sorry, I didn’t mean to imply (didn’t think I implied) it was a blogosphere myth that the most likely value of climate sensitivity was 3 degrees. You’re right that’s the consensus for the most likely value. The myth I was referring to was the idea that the cluster around 3 degrees in the Stainforth et al results somehow gave support to this value, which Richard seems to be convinced was our “real” result (and in which case his programme would have made complete sense).

But you’re right, it’s just an example of what can go wrong, and there is no point in getting lost in the details of who thought what when and why (in self-defence, I only got dragged back into this one because Richard popped up).

I’m not sure I agree with you that Stainforth et al told us nothing about sensitivities greater than 7, given that no-one had reported GCMs behaving like that before so these fat tails could, until then, have been dismissed as a simple-modelling artifact. But that would bring us dangerously close to discussing climate sensitivity, which is off-topic.

I’m afraid I’ll have to drop out of blogging for a few days: it’s been an interesting weekend, which has left me with a much better impression of blogs than I had before, not least because of your very measured moderation (particularly impressive in view of my article – someone told me you had to be provocative to be noticed in the blogosphere). Thanks, and enjoy the rest of the discussion. Let me know what you all decide to do (if anything).

Regards,

Myles

93 · TonyN Says:
7 April 2008 at 8:11 AM

It’s a pity that Myles Allen has had to drop out.

I would have liked to ask him why he thinks that testimonies obtained by Fiona Fox (comment 50) from journalists who attended his 2005 press briefing are reliable evidence of what happened when she had so obviously jogged their memories. It would also be interesting to see the whole letter, rather than just a single paragraph.

Richard Black’s coverage for the BBC can be found here:
http://news.bbc.co.uk/1/hi/sci/tech/4210629.stm

An interview with Myles Allen on the BBC’s Today programme on 27th Jan 2005 can be found here:
http://www.bbc.co.uk/radio4/today/listenagain/ram/today1_climate_20050127.ram

A transcript from Simon Cox and Richard Vadon’s BBC Radio4 programme ‘Overselling Climate Change’, including the interview with Myles Allen, can be found here:
http://ccgi.newbery1.plus.com/blog/?p=70

116 · stefan [Rahmstorf] Says:
10 April 2008 at 1:07 AM

Dear Myles,

thanks for coming over here to discuss this issue with us.
In my view our contentious sentence “we feel that the most important result … is that by far most of the models had climate sensitivities between 2ºC and 4ºC” is not wrong, it is certainly not an indication of a lack of fact checking at RealClimate, and also it is not a criticism of your paper. Rather it is a valid interpretation of your results. Other scientists may interpret your or my data differently – this is sometimes annoying but part of a healthy scientific discourse. Even today I still think that this in fact is your most important result. Let me try to explain.

You argue that you started from a model with about 3 ºC climate sensitivity, and then randomly perturbed parameters in all directions – so of course the peak of your distribution is near 3 ºC. I agree with that. As you know we also work with model ensembles, and what I found the most interesting question both with our own and with your ensembles is: how broad is this peak? I.e., how quickly do you get away from those 3 ºC when you change the parameters? How strongly do you need to tweak a model to get a really different climate sensitivity? Note that we did not write that the most interesting result is that you get a peak near 3 ºC – we wrote that the most interesting result is that most models remain inside the range 2-4 ºC when you perturb the parameters. I still find this small spread far more interesting than the outliers.

Concerning the outliers, my prior expectation (and maybe this is where we differ) is that a model version with 11 ºC climate sensitivity is very likely just an unrealistic model, which would fail a number of quality checks – we discuss this in detail in our original post. This is why per se I do not find those tails very interesting – yes, by tweaking parameters enough I can get a model to behave very strangely, but so what? I certainly would not go to the mass media suggesting that 11 ºC could be a realistic climate sensitivity (not even as an extreme case of a wide range), before I had performed some pretty rigorous testing on these high-sensitivity models. (Now this is a criticism – not of your paper but of your media outreach.) If I had a climate model with 11 ºC climate sensitivity that had passed the kind of validation tests discussed in the IPCC report – e.g., which gives a realistic present-day climate, including seasonal cycle, a realistic response to perturbations like the Pinatubo eruption, a realistic 20th-Century climate evolution and a realistic Ice Age climate – well, then I would call in a press conference. But I don’t think anyone has ever produced such a model.

Thanks also to all the other contributors to this discussion – I think this is excellent, and a good advertisement for science blogging.

[19/04/2008 TonyN says: Myles Allen has not returned to the discussion]

So what does all this add up to?

I find it astonishing that, after three years, Myles Allen should continue to try and defend a press release that is clearly indefensible. It seems even more extraordinary that an experienced researcher who played an important and sensitive role in the IPCC’s 4^th Assessment Report should attempt to justify his position by citing the testimonies collected by Fiona Fox. This kind of evidence, where words have so clearly been put into the witness’ mouths, would not be accepted in a court of law, or anywhere else that I can think of. I sincerely hope that it would not be acceptable at the IPCC.

But above all, I fear that Myles Allen doth protest too much.