## Monday, April 14, 2008

### British Antarctic Survey: evidence against AGW

Joseph D'Aleo has informed me about this rather fascinating page written by the British Antarctic Survey (BAS) and describing the impact of the Antarctic data on the climate change debate:
Climate change: our view (BAS)
The page was created in December 2007, the month when William Connolley, an official of the Green Party who contributes to RealClimate.ORG, left the BAS.

It seems likely that the page was written by several people. It begins with some well-known as well as less well-known facts about the Antarctic climate. It continues with the shocker to be discussed below and finally it ends up with some generic IPCC newspeak saying that we are pretty sure that climate change is man-made.

What is the shocker? Well, it is a paragraph in the middle of the page - search for "As part" - that pretty much says the opposite thing. Let me copy it in its entirety.
As part of the work undertaken for the Fourth Assessment Report of the IPCC [13], about 20 different climate models were run with historical changes to natural and anthropogenic forcing factors to simulate the climate of the 20th century. The simulated changes in Antarctic surface temperatures over the second half of the 20th century vary greatly from model to model with no single model reproducing exactly the observed pattern of change. However, when results from all models are averaged, the resulting pattern of change bears some resemblance to that observed, with greatest warming in the Peninsula region and little change elsewhere [20]. This result suggests that some of the observed change may have an anthropogenic origin, but the lack of a clear and consistent response to changed forcing between models also suggests that much of the observed change in temperatures may be due to natural variability. The IPCC model experiments fail to reproduce some of the observed features, notably the rapid warming of the lower atmosphere. These differences between modelled and observed changes could be used to argue against attributing change to anthropogenic forcing but some caution is called for as the models used may not adequately represent all of the complex processes that determine temperatures in the polar regions.
Boldface added by TRF. Once again, they compared the observed data against 20 models. Those models generated a lot of incoherent predictions that can be called noise once the following observation is taken into account. Even though the models have arguably had different values of the CO2 sensitivity and other things, neither of them was close enough to reality. Their average was doing better - although many of the characteristic fingerprints still come out incorrectly. While this may indicate that some portion of the climate change is man-made, the bulk of the observed changes - and the bulk of the predicted changes and their detailed structure - have nothing to do with the quantities in which the models differed, such as the overall CO2 climate sensitivity. The latter seems to be uncorrelated to the observed change.

The final paragraphs were either added by a partisan or by a person who wanted his or her colleagues to appreciate the fact that the British Antarctic Survey is largely paid from the climate hysteria funds. These paragraphs selectively mention two phenomena - the strengthening westerlies that seem to agree with the models (unlike most other quantities) and the collapse of the 12,000-years-old Larsen-B ice shelf in 2002 - and even though these two phenomena cannot be used as evidence of the man-made origin of climate change, they are being used in this manner anyway.

I would guess that the arguments of the BAS fellows about the wording of this document had to be unusually violent because the text seems to be a result of a classic clash between scientific integrity and political manipulation of science. And despite Connolley's partisanship and ignorance concerning the latent heat of ice, I am actually not 100% certain where he was standing in this BAS civil war.

And that's the memo.