Monday, July 03, 2006

Lying with facts

Whilst wandering around the web today, I stumbled across this post from Tree Hugger talking about global warming. I just want to address 1 little part of it.
Facts: Every year since 1917 has been warmer than 1917.

That's the kind of thing you say when you're trying to make a case for something that isn't true. Or if you want to make a case for something that may be true, but the evidence is ambiguous. It's an attempt to make a fact sound suspicious and/or meaningful. Let's assume that it is, in fact, true, and try to look at what it means. Another way of putting that would be this - "the coldest year of the last 90 was 1917." That's all it means.

And the real fact is this - one of those 90 years has, by definition, to be the coldest in the data set. Whether the globe is getting warmer or colder, take any 90 year stretch, and one will be the coldest. Take any stretch of any number of years, and one will be the coldest. So you look at the last 100, 200 years, figure out which one was the coldest and set the data set to start from there. Is 1917 the coldest year of the last 90? Apparently. Of the last 100? 150? 200? I don't know. For all we know, it was the coldest of the last 500, and the 90 year range was cherry-picked so it could be expressed in exactly the way it was expressed, cherry-picked and presented to seem meaningful.

So, in the last 90, the coldest year was 1917. Period. That fact has no probative value whatsoever in determining whether the planet is warming, and leading off with that kind of a fact almost defeats the argument before it even gets started. You look at that and wonder "where's the real evidence, and why is the argument starting with this sleight of hand?"



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