The Emporer Nero Award
BeeDubs (nom de plume of Will Billcox?) asks about the recent hockey stick controversy. The background is differences between reconstructions of the history of the planet's surface termperature shown in this figure:
You can see that there are many such reconstructions. They are not easy to make. Some attempts had regional biases towards for example Europe where there were good records. The little ice age was associated with a recession of european culture, hard times for the settlers on Iceland, etc. and may have been a regional phenomenon, hence the different estimates above. Some attempts use bristlecone pines which have been called into question, others use corals or isotopes in ice cores. One of the most widely accepted climate histories is the dark blue line in the figure above which is pretty steady and then shoots up right at the end-- the famous hockey stick, due to Mann and coworkers. Recently Hans von Storch (who was our guest at the university not so long ago, a nice guy, mathematician by training) has questioned the validity of the algorithm used to obtain the hockey stick, arguing that it artifically supresses variability in the temperature record. von Storch could give noise to the algorithm and end up with a hockey stick and so the argument goes, what is it good for? RealClimate has published a rebuttal so I won't go into the technical details here. Here is a summary from Wikipedia:In 2006, a panel report of the National Academy of Sciences ordered by the U.S. Congress was published. The basic conclusion of Mann et al. (1998, 1999) was that the late 20th century warmth in the Northern Hemisphere was unprecedented during at least the last 1,000 years. This conclusion has subsequently been supported by an array of evidence. The committee found it plausible that the Northern Hemisphere was warmer during the last few decades of the 20th century than during any comparable period over the preceding millennium. However the panel expressed reservations that uncertainties make it difficult to compare individual years and decades of the 20th century with any similarly short period prior to around 1600.
The report also confirmed some of the points of the criticism by M&M: the bristlecone pines are not a good temperature proxy; the data and the software should have been made available; and the principal component analysis as used by Mann et. al. "tends to bias the shape of the reconstruction", however this "does not appear to unduly influence reconstructions of hemispheric mean temperature" [23].
My take on the debate is that the debaters are trying to throw up a smoke screen. The historical climate is fairly important and interesting, but it is not useful after the late 1800s when people started to have thermometers. After that point we have a quite accurate temperature record; the temperature rise from then to now is shown in the graph above. And so I give today's award in misdirection, named after Emporer Nero who fiddled while Rome burned, to those who try to discount climate change using the hockey stick argument.
posted by Matt_J @ 1:45 PM
3 Comments:
It is important to note that there is an official definition regarding the curvature of hockey sticks. The rule is that if you lay the stick flat on the ice with the blade curved down, a dime standing on end should not be able to pass between the blade and the ice.
Even with the little ice age included, the stick is a stick.
I lot of the time I don't even try to listen to the political debate. It is so polarized and processed. The science is much more interesting-- and of course part of why it is interesting is the political implications-- but I leave that side of it to others.
This is classic case of the political engine distorting the science. Hans von Storch criticizes the Mann hockey stick. Pundits use this to support their claim that anthropogenic climate change is bunk, when really all it is is a technical discussion concerning statistical methods. Here is what Hans von Storch himself says (http://energycommerce.house.gov/108/Hearings/07192006hearing1987/Storch.pdf):
'I conclude that the claim of 'detection of anthropogenic climate change' is valid independently of which historical temperature reconstruction one chooses to believe in.'
And,
'Based on the scientific evidence, I am convinced that we are facing anthropogenic climate change brought about by the emission of greenhouse gases into the atmosphere.'
The full link (remove line spaces before using!):
http://
energycommerce.house.gov
/108
/Hearings
/07192006hearing1987
/Storch.pdf
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