If you have been reading about hockey and the polarized arguments, charges & counter charges, and name calling, you might not be reading about the NHL strike. The real hostility has been the debate regarding the global warming “hockey stick,” a graphic that has become the poster child for the environmental movement. Published by Michael Mann and colleagues in 1998 and 1999, the graphic shows that the climate of the Northern Hemisphere had been remarkably constant for 900 years until it suddenly began to heat up about 100 years ago–right about the time that human use of fossil fuels began to push up levels of atmospheric carbon dioxide. The overall shape of the curve resembles a hockey stick laying on its back-a straight part with a sudden bend upwards near the end. This would be dramatic, if it were true that is.

Professor Mann is a scientist using scientific methods so one would assume that there wouldn’t be much debate. Either the underlying data is correct or it isn’t, right? Unfortunately, it’s not that simple. An accurate thermometer wasn’t invented until 1724 (by Fahrenheit), and good worldwide weather record keeping didn’t exist prior to the 1900’s. For earlier eras, we have to depend on indirect estimates called proxies. These include the widths of tree rings, the ratio of oxygen isotopes in glacial ice, variations in species of microscopic animals trapped in sediment (different kinds thrive at different temperatures), and even historical records of harbor closures from ice. Of course, these proxies also respond to other elements of weather, such as rainfall, cloud cover, and storm patterns. Moreover, most proxies are sensitive to local conditions, and extrapolating to global climate can be hazardous. Chose the wrong proxies and you’ll get the wrong answer. Herein lies the basis for the debate.

Even worse, data available to Mann and his colleagues had to be averaged, interpolated, and extrapolated. That required subjective judgments which unfortunately could have biased the conclusions. More importantly, this improper normalization procedure tends to emphasize any data that does have the hockey-stick shape, and to suppress all data that does not. When others fed these random data into the Mann procedure, out popped a hockey-stick shape! Let me state that again, if one puts in any data, even random data, into the procedure that is at the heart of the Global Warming debate, you get a hockey stick shape. In other words, the hockey stick graphic proves nothing.

However, since the general population (let alone C.U. Ethnic Studies students taught by Ward Churchill) are not going to understand “principal components analysis, detrended standard deviations and autoregressions,” pretty charts and short sound bites become very influential in driving public opinion and governmental policy. With that in mind, here’s an Independent Sources sound bite for this controversy: “the hockey stick shows us that there has been a dramatic increase in bad science in the late 20th Century. In fact, the last decade of the 1900’s had more bad scientists doing more flawed analyses to promote their biased agendas than any time in the previous 1000 years” (and Independent Sources has the graphic to prove it!).

This entry was posted on Friday, March 11th, 2005 at 5:32 am by Insider and is filed under Brilliant, but uncategorizable. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.