Tuesday, July 14, 2009

Math is Math

El Nino 2009Looks like this will be an El Nino year, perhaps a strong one, which pleases some for the schadenfreude it provides:
1998 was the hottest year on record because of an extraordinarily powerful el Nino that heated up the entire planet dramatically. But because it was so hot, climate disruption deniers have been using it as the starting point from which they claim, wrongly, that “the global temperature has been cooling for a decade now.” This false claim was strengthened by the lucky coincidence that 2008 turned out to be a la Nina year, when the global temperature dropped significantly. Climate disruption deniers then took advantage of an unfortunate fact of least-squares linear trend estimates - they’re VERY sensitive to endpoint variation, especially in short, noisy datasets. And not only is global temperature noisy on a monthly and yearly basis, but ten years is a woefully short amount of data. And don’t even get me started on Joe D’Aleo’s, Lord Monckton’s, and Ross McKitrick’s 5-year “trend” from 2003 to 2008 which, conveniently enough, has another el Nino to la Nina transition.

So now, with a new el Nino heating up the summer and autumn global temperatures by some as-yet-unknown amount, climate disruption scientists and activists have their own convenient endpoints to the data. 1999 was a la Nina year, after all, and 2009 is an el Nino year, so any trend calculated from 1999 to 2009 will be huge, given that global temperatures for July through December are significantly warmer on average than January through June. It’s not outside the realm of possibility that 2009 could be warm enough to turn the supposed “cooling trend” into a “warming trend” all by itself. And that’s the first reason I’m happy about a new el Nino.

Of course, we’re talking weather here, not climate, and the exact same statistical tools that I and others use to debunk the bogus cooling trends touted by deniers could be used against any climate scientist who touts a hot 2009. But that brings me to the second reason I’m happy about el Nino - I’m actually looking forward to climate disruption deniers screaming “a hot year in 2009 is only weather, the cooling trend since 1998 is a real trend!” Because in return, I get to call the denier a hypocrite.

Math is math, after all. If the data statistics says that there’s too much noise in the data to extract a meaningful trend from 1998 to 2008, the the same will almost certainly be true from 1999 to 2009. And as a result, any denier who looks at the 99-09 trend and says “that’s just weather, not climate” or “the trend has endpoint problems that make it inaccurate” or even “you cherry-picked your endpoints” will immediately be revealed as a liar and a hypocrite.
Yes, it will be amusing to see the responses from those who confuse weather and climate, have been shouting about supposed global cooling, how Al Gore got it wrong, how cold spring has been this year, blah blah. No, I won't link to them, but they're easy to find if you search on something like "global cooling trend".
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