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The Long, Hot Winter
March 13th, 2007 · 3 Comments
A lot of us in the U.S.A. just went through a rather chilly February.
It wasn’t a record-breaker; in fact, according to NOAA it was the 34th-coldest February out of 113 on record. I’ve seen a lot of Februarys, and I’ve seen colder. But it was pretty chilly.
Some people have remarked that this is evidence against the reality of global warming. I point out to them that nobody in his right mind ever claimed that we can’t still have cold months, especially in limited areas, and the that good old USA is less than 2% of the surface area of the planet. If we want to know about global warming, we shouldn’t be talking about one month, we should be talking about the last 30 years or more (at least). And we shouldn’t be talking about just the USA, we should be talking about the whole world.
NASA’s Goddard Institute for Space Studies (GISS) regularly updates their monthly mean global temperature data; we now have data through February 2007. Here’s the latest graph (each dot is the global average temperature for one month, the red line is a 5-year smooth using a wavelet transform):
giss.JPG
The overall trend is easier to see if we magnify the temperature axis. This will send some of the individual data points “off the scale,” but the trend will be much clearer:
giss2.JPG
In case you’re interested, according to GISS data during the modern global warming era (from 1975 to the present) earth has been warming at a rate of about 0.0185 deg.C/yr (1.85 deg.C per century). Taking uncertainties into account, we should say 1.85 pm 0.4 ^circC/century.
But I’m really wondering about this February. It turns out that, according to GISS data for the planet earth, this February did not show “record low temperatures.” In fact it’s closer to a record high — a lot closer to a planetary high than the U.S. was to a national low. This February was the 5th-hottest on record. The five hottest Februarys on record are (in order): 1998, 1995, 2002, 2004, and 2007.
But that’s not all the heat we’ve been feeling lately. Many of us in the U.S. remember the exceptionally warm January this year. This was not just an American phenomenon. It turns out that January of this year was the hottest ever. The five hottest Januarys on record are (in order): 2007, 2002, 2005, 2003, and 1998.
As a matter of fact, GISS data indicate that worldwide, this January was the hottest month (not just the hottest January) ever.
Again, many of us remember the very warm December in America which preceded the record-warm January. This too was a world-wide phenomenon; December was the hottest ever recorded. The five hottest Decembers on record are (in order): 2006, 2003, 2005, 1997, 2004.
Climatologically speaking, the month of December-January-February make up northern-hemisphere winter (southern-hemisphere summer). So this last season, world-wide we’ve just been through: the hottest December ever, the hottest January ever, and the 5th-hottest February ever.
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