by Judith Curry

I’m not sure what the IPCC expected when they leaked their report to ‘friendly’ journalists, but I suspect that it was not this article by David Rose,

People have been asking me to comment on the leaked IPCC Final Draft Summary for Policy Makers. Apparently someone in the IPCC made the Report available to ‘friendly’ journalists, as part of a strategy to brief them before the formal release of the Report. I have declined to comment until very recently, since I thought it was best to let the IPCC process play out. Now it is clear that the leaked report has made it into the hands of journalists that were not on the IPCC’s ‘friends’ list. I have now seen a copy of the SPM, and I provided comments to David Rose (and also to another journalist, not sure when that will air).

David Rose quotes me in his article (accurately). I provide below the complete text of the email response I sent to David Rose:

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What interests me the most about the AR5 report is how the IPCC is changing its positions and statements relative to the previous AR4 report. It is particularly interesting to see how the different drafts of the AR5 Summary for Policy Makers are changing. I am very grateful that these drafts have been leaked, as these drafts provide important insights into the reasoning behind the IPCC conclusions and confidence levels. The IPCC should of course change its conclusions and confidence levels in response to new scientific evidence and analyses. Because of the rapid pace of publication of papers over the past year that challenge aspects of the AR4 conclusions, the slow ponderous assessment process of IPCC has been apparently having difficulty in responding to and assessing all this, as evidenced by the substantial changes in the drafts.

My main point is this. If there are substantial changes in a conclusion in the AR5 relative to a confident conclusion in the AR4, then the confidence level should not increase and should probably drop, since the science clearly is not settled and is in a state of flux. While there has been a reduction in either the magnitude of the change or in a confidence level in some of the supporting findings, these changes do not seem to have influenced the main conclusion on climate change attribution:

It is extremely likely that human influence on climate caused more than half of the increase in global average surface temperature from 1951-2010.

The ‘extremely likely’ represents an increase in confidence from the ‘very likely’ of the AR4. An increase in confidence in the attribution statement, in view of the recent pause and the lower confidence level in some of the supporting findings, is incomprehensible to me. Further, the projections of 21st century changes remain overconfident. These inconsistencies seems to me to reflect a failure in meta-reasoning by the IPCC. I hope that these inconsistencies are pointed out at the forthcoming meeting in Stockholm.

I have previously argued that the consensus seeking process used by the IPCC acts to create and amplify biases in the science. I have recommended that the consensus seeking process be abandoned in favor of a more traditional review that presents arguments for and against, discusses the uncertainties, and speculates on the known and unknown unknowns. I think that such a process would better support scientific progress and be more useful for policy makers.

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Here is the main relevant text on the SPM from Rose’s article:

What they say: ‘The rate of warming since 1951 [has been] 0.12C per decade.’

What this means: In their last hugely influential report in 2007, the IPCC claimed the world was warming at 0.2C per decade. Here they admit there has been a massive cut in the speed of global warming – although it’s buried in a section on the recent warming ‘pause’. The true figure, it now turns out, is not only just over half what they thought – it’s below their lowest previous estimate.

What they say: ‘Surface temperature reconstructions show multi-decadal intervals during the Medieval Climate Anomaly (950-1250) that were in some regions as warm as in the late 20th Century.’

What this means: As recently as October 2012, in an earlier draft of this report, the IPCC was adamant that the world is warmer than at any time for at least 1,300 years. Their new inclusion of the ‘Medieval Warm Period’ – long before the Industrial Revolution and its associated fossil fuel burning – is a concession that its earlier statement is highly questionable.

What they say: ‘Models do not generally reproduce the observed reduction in surface warming trend over the last 10 – 15 years.’

What this means: The ‘models’ are computer forecasts, which the IPCC admits failed to ‘see… a reduction in the warming trend’. In fact, there has been no statistically significant warming at all for almost 17 years – as first reported by this newspaper last October, when the Met Office tried to deny this ‘pause’ existed.In its 2012 draft, the IPCC didn’t mention it either. Now it not only accepts it is real, it admits that its climate models totally failed to predict it.

What they say: ‘There is medium confidence that this difference between models and observations is to a substantial degree caused by unpredictable climate variability, with possible contributions from inadequacies in the solar, volcanic, and aerosol forcings used by the models and, in some models, from too strong a response to increasing greenhouse-gas forcing.’

What this means: The IPCC knows the pause is real, but has no idea what is causing it. It could be natural climate variability, the sun, volcanoes – and crucially, that the computers have been allowed to give too much weight to the effect carbon dioxide emissions (greenhouse gases) have on temperature change.

What they say: ‘Climate models now include more cloud and aerosol processes, but there remains low confidence in the representation and quantification of these processes in models.’

What this means: Its models don’t accurately forecast the impact of fundamental aspects of the atmosphere – clouds, smoke and dust.

What they say: ‘Most models simulate a small decreasing trend in Antarctic sea ice extent, in contrast to the small increasing trend in observations… There is low confidence in the scientific understanding of the small observed increase in Antarctic sea ice extent.’

What this means: The models said Antarctic ice would decrease. It’s actually increased, and the IPCC doesn’t know why.

What they say: ‘ECS is likely in the range 1.5C to 4.5C… The lower limit of the assessed likely range is thus less than the 2C in the [2007 report], reflecting the evidence from new studies.’

What this means: ECS – ‘equilibrium climate sensitivity’ – is an estimate of how much the world will warm every time carbon dioxide levels double. A high value means we’re heading for disaster. Many recent studies say that previous IPCC claims, derived from the computer models, have been way too high. It looks as if they’re starting to take notice, and so are scaling down their estimate for the first time.

Twitter warfare is breaking out, the main issue of contention is Rose’s statement:

What this means: In their last hugely influential report in 2007, the IPCC claimed the world was warming at 0.2C per decade. Here they admit there has been a massive cut in the speed of global warming – although it’s buried in a section on the recent warming ‘pause’. The true figure, it now turns out, is not only just over half what they thought – it’s below their lowest previous estimate.

There is a bit of an apples and oranges comparison issue here, relative to the period for which there has been or is projected to have a 0.2C per decade increase.

Another article on this topic is a post today by Bjorn Lomborg Global Warming Without Fear.

Personally, I think these leaks are a good thing. An even better thing would be to make all formal drafts publicly available so that they can be discussed. Pressure from the MSM has resulted in the pause being mentioned in this draft (but not the previous ones). The best thing, IMO, would be to abandon the entire IPCC process, and have the AR5 be the final report.