Friday, November 16, 2012

"Data" does not necessarily prove climate models wrong

The post I did showing that instrumental approaches to climate sensitivity are in the same ball park as other approaches was dismissed by a  contrarian because computer models are involved in some of the papers I identified.

It is absurd to impose a blanket ban on climate models. They are not infallibly right, but neither are they infallibly wrong. By dismissing them out of hand, contrarians are more or less saying that climatology should go back to the 19th century, when thousands of calculations had to be done "tediously" by hand. To call this line of contrarian argument "Luddite" would be a grievous slur on Ned Ludd.

Anyway, this dismissal has sent me off into a study of climate models - something I have avoided pretty much up to now, apart from reading and reviewing A Vast Machine by Paul N Edwards.

I will post my findings later, but today I hit on a nice piece  here: the modelers pressed toward greater precision, their progress faltered. No matter how they tried to tweak their models, the computers could not be forced to show the full extent of the Northern Hemisphere cooling recorded in the 1940s and 1950s. Finally in 2007 a careful analysis revealed that the global data had been distorted by a change in the way ocean temperatures were measured after the Second World War ended. The models had been better than the observations.(92*)....During the war most measurements were by US ships which measured the temperature of water piped from the sea into the engine room. But after 1945 a good share of data came from UK ships, which dipped a bucket in the ocean; the water in the bucket cooled as it was hauled aboard, Thompson et al. (2008). Note that in IPCC (2007b), p. 11, the 1940s-1950s is the only element of the 20th century temperature record that the models failed to match.

I read elsewhere that part of the problem was that the water was also warmed by heat radiating from the engine room as it was sucked into the ship.

A similar episode happened in the 1990s when satellite records showed cooling when everything else showed warming. Spencer and Christy made immense amounts of skeptical hay from this until it was shown that the "cooling" was caused by decay in a satellite's orbit.

These are just anecdotes, but they do remind us of the robustness of climate science generally, and a clash between models and data does not necessarily prove the models wrong.

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