Testimony at the UK IPCC 5th Assessment Review

The UK's Energy and Climate Change Committee held its first evidence session into the IPCC 5th Assessment Review (AR5) on January 28, 2014. The invited witnesses gave oral testimony in two sessions:

Panel 1:

Panel 2:

Panel 1 presented the views in support of the conclusions of the Intergovernmental Panel on Climate Change (IPCC). Panel 2 presented the view that the temperature projections of the IPCC are greatly exaggerated.

The oral evidence is presented HERE. A few highlights are given below.

Panel 1:

In response to a question about the main changes in AR5 compared to the previous review:

Professor Sir Brian Hoskins: "For the first time we can measure the decrease in the ice sheets in Greenland and Antarctica and see their contribution to sea level, so the present 3 millimetres per year of rising sea level. About a third of that is due to the decrease in the Greenland and Antarctic ice sheets. ... The changes in the climate system are consistent with the increase in greenhouse gases."

[The panel failed to note that evidence of warming and sea level rise is not evidence that greenhouse gases caused those changes.]

Dr Stott: We have known for a while that it is not just simply a matter of increasing greenhouse gases in the atmosphere producing a warming; that there is potentially some effect from aerosols, notably a net cooling effect. The overall warming effect would have been larger than observed were it not for some cooling effect from the aerosols. That is all factored into the assessment, including of climate sensitivity and transient climate response.

Question: "I understand that the full technical report scales down the projections for near term global warming by 40% below that which the CMIP5 global climate models gave. Is that correct and why is not mentioned in this Summary for Policymakers?

Dr. Stott: "In terms of the near term, there is a scaling of approximately 10%, which is an estimate in terms of the comparison between the observed trends and the model trends."

Q12: "The figures from the models are a range of between .48 ºC and 1.15 ºC and the figure in the technical report is revised down to 0.3 ºC to 0.7 ºC. That is a 40% reduction against 10%."

Professor Allen: "The aim of the Summary for Policymakers was to summarise what we thought was most important rather than the detail.  The key point is there is an enormous amount of judgment in running climate models. There is nothing sacrosanct about ranges that come out of the CMIP5 ensemble."

[The Panel 1 scientist argue that the 40% reduction from climate models to the IPCC short term projections to 2035 is a detail that is not important for policymakers.]  

Panel 2:

Professor Lindzen: "I do not find very much of concern. What I find is a translation problem. For instance, I don 't agree with the arguments for attribution but, on the other hand, if man is responsible for 51% of the warming since the last 50 to 60 years, that itself does not tell me that the sensitivity is high. It is completely consistent with there not being a problem. ... in the US the reward for solving a problem is to have your funding ended, so there is an intrinsic pressure to make sure a problem never disappears. ... My colleague Carl Wunsch, who is very much involved with TOPEX and the current measurements, feels you cannot say anything about that [sea level rise] at the moment because you have two different measurement systems and they have not yet been fully reconciled and so we are not sure what is going on with the sea level. Using the previous measurements, we do know that it has been increasing for thousands of years at a certain small rate and indeed there is some reason to suppose, whether you had global warming or not, you might want to take that into account in how you develop land and so on. I don 't see much evidence here that points to man doing something extraordinary."

Nicholas Lewis: "A major concern with the IPCC AR5 report is that the observational evidence is pointing in one direction and the model simulations, particularly for the future, are pointing in a somewhat different direction towards substantially higher warming than the best observational evidence in AR5 implies. ... I do not think they [climate models] reflect the current evidence. There was reference made in the first panel to the reduction in the aerosol cooling effect strength in AR5 compared with previous assessments due to better knowledge. In some ways that is the most significant thing in AR5 because if aerosol cooling is lower and, as Mr Lilley said, we would know how much warming there has been, then it must follow that less of that warming is attributable to carbon dioxide .... That was not recognised at the time when they started drafting AR5 and it certainly was not taken into account in the models, because they predate this reassessment of the evidence. ...The big thing that has changed is they now have much better estimates of things like aerosol forcing, in particular the cooling effect due to having satellite-based studies and other studies of working out what its effect is. If that is substantially lower it has come down from 1.3 º to 0.9 º since AR4 it necessarily implies that the warming from greenhouse gases must be substantially less than previously thought....I think that those [temperature] projections, while they are within the range of possibilities, are probably centred about 60% higher than they would be if they were based on the observational evidence in AR5."

Donna Laframboise: "You start with thousands of research papers and then a report 14 chapters long gets written from those thousands, so there is a lot of human judgment to decide what is relevant and important. Then we have 14 chapters condensed down to 31 pages and so, again, there is a whole other level of human judgment. Human judgment, of course, is not science. The science was way back at the beginning before the papers were written and then the chapters of the IPCC report were written and then the summary was written. If it were a scientific document, we would expect that the summary written by the scientists would be the last word and that is what would be released to the media and the policymakers, but instead it is almost like it is a summary by policymakers because then there is a four-day process where every single line in that summary written by the scientists is argued over and it is behind closed doors .... If there is no political pressure and everything is fine, why isn 't that four-day meeting open to the public? Why isn 't it televised? Why are there not media present if it is simply a discussion and a dialogue between policymakers and the scientists who have done the summary? ...   I am suggesting that there is a potential for politics to influence the emphasis. ... The chairman of the IPCC has gone around for years publicly declaring that the entire report is based 100% on peer-reviewed literature. In fact that is not the case. About a third of the sources cited were not peer-reviewed literature and thousands of people who worked on the IPCC report knew that, but none of them talked to the media and none of them protested that the chairman was misrepresenting the process. ... What I see is there are so many questions and biases and potential problems with the IPCC process that I do not think it is trustworthy."


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