Friday, January 2, 2009

Climate change is not linear

The fact that winter was unusually cold this year seems to have led some to conclude that global warming is a scam.

The problem is, temperature change is not a simple linear phenomenon. Here is a graph of global temperatures over the last 150 years, normalized to the 1961-1990 mean:

Notice the few red years to the left, and the few blue years to the right. Not every year is clearly above or below the mean as we might expect.

For more on a good, short rebuttal to the skeptics, check here.

The story mentions the International Climate Science Coalition (ICSC), a group of climate change skeptics. They got together recently to sign the Manhattan Declaration against the "climate change consensus". I found the list of "climate experts" who signed to be quite entertaining. A random choice, William M. Briggs, PhD, finds a statistician at a New York hospital whose resume has no mention of climate work since 1998, while getting his PhD. Statistical knowledge is of course important for the study of climate science, but I would hardly call him a "climate expert".

Some controversy arose earlier this year when it was found that a data repository on world temperatures was reporting a few areas incorrectly in October. Of course, once the problem was fixed, it still turned out that October was a really warm month.

As any reader of this blog no doubt knows, I am not a fan of confusing causation with correlation. There is no direct, causal evidence that man is impacting the environment, nor, I expect, will there ever be. But, even without the smoking gun, the evidence is so strong that to think we're not a part is ludicrous.

For more, check out the even more detailed How to Talk to a Climate Sceptic.

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