Temperature Anomalies and Global Warming

Weather Underground updates this map every month.



It shows the temperature anomalies around the globe for January 2009 relative to the average between 1961 and 1990. As has usually been the case over the last ten or fifteen years, the global average temperature was above average for the month; it was the 7th warmest January on record, in fact. (And look at Siberia: it's been looking like that a lot lately - the climate seems to be changing there really dramatically.) However, among the few areas of the world that were below average were Western Europe and the Northeastern and Midwestern United States. For the US as a whole, it was only the 59th warmest January out of the last 114. (Note, too, the coolish temperatures over the central Pacific: a symptom of La Nina.)

One inevitable consequence of cold snaps during the winter is that global warming skeptics will say sarcastic things about the weather. And some people become more receptive to denialist claims - claims by people like George Will who recently wrote a denialist editorial that was pretty much entirely composed of falsehoods. But of course the fact that the temperature of the planet is gradually rising doesn't mean there will never again be any temperatures anywhere that are below average - and you can see clearly enough that a significant cold snap in some of the densely populated parts of the industrialized world is perfectly consistent with the world having temperatures somewhere in the neighborhood of the 5% warmest ever.

Ricky Rood makes a related point at his blog on Weather Underground, where he shows these maps of the continental US temperature anomalies from the Januaries of 2008 (top) and 2009. It so happened that in 2008, most of the big cities in the US were warmer than average, and this year they were colder (the major exception being the cities on the west coast). Overall, though, the months were similar for the country as a whole, and near average. But for two reasons, the denialists have had more fodder this year: 1) the colder weather disproportionately hit the places where lots of people live - if the map were a cartogram (which would make no sense) it would be overwhelmingly blue, including in big media centers where opinions tend to get amplified; and 2) the colder weather this year hit places that are naturally colder, which makes it seem more dramatic. Record lows in Oregon are gonna be chilly for the folks there, but not freezing; it's a lot more startling when it hits -40 degrees in Maine. As Rood says, "I don’t remember a lot of rhetoric that 'global warming is spurious' coming out in 2008, from say, Seattle."

Well, these points probably seem obvious to most people. And for that committed minority who don't believe in anthropogenic global warming, there is an entire industrial-media apparatus (of which George Will is obviously a card-carrying member) designed to confirm their views, and no amount of data is likely to win them over. But maps like these are still a good corrective to the impulse we all have to extrapolate global trends from the anecdotal events we read about in the news.