Tuesday, July 25, 2006

Heat wave not the same as global warming

[updated below]

Critics of prudent measures designed to fight climate change have made a great big stink about the fact that there are natural cycles and that so far the increase in temperature over the last century (about 0.6 degC) is within that natural variation (never mind that the rate of increase over the last century is off the chart). If you want a rather shameful example of this line of reasoning among conservative evangelical Christians, see the Interfaith Stewardship Alliance and its Cornwall Network.

They have also made naive and silly comments, whenever a big snow storm or a cold shock sweeps through an area, that certain weather events belie "global warming."

Some of those who are rightly concerned about climate change are also at fault for blaming every heat wave on global warming. This is equally incorrect. Climate is not the same as weather.

Bill Patzert, a climatologist at the Jet Propulsion Laboratory, makes the distinction, in an article from the San Gabriel Valley Tribune:
Don't blame the seemingly endless heat wave just on global warming - this one's the product of a high-pressure system to the east and California's rapidly expanding growth, said Jet Propulsion Laboratory climatologist Bill Patzert.

Together, he said, they have combined to push the temperature 12 to 16 degrees Fahrenheit above normal.

"Of the 12 degrees, how much is global warming? I would say 1 degree," Patzert said. "The other 11 degrees is meteorology" and lots of new heat-soaking pavement and other developments.

As in most mid-summers, a region of high pressure over Arizona and New Mexico is pulling hot, moist air from the Mexican desert.

But this summer, Patzert said, "it's so intense it's actually included us in the pattern. It's kept the marine layer off the coast, what I call Southern California's air conditioner."

"We didn't get any May Gray and June Gloom, so we kind of skipped spring," he said.

But what has made these conditions especially unbearable, Patzert said, is the new face of California's landscape, repaved by ever-expanding development.

"As soon as you start putting in agriculture, golf courses, especially housing developments, it starts to retain heat. The nights are not cooling. That's why we get warmer and warmer temperatures by mid-afternoon, because we're starting warmer," he said.

Either way, it is people's actions that are the problem. It's time to start making moral choices about how we want to live our lives, and these choices are going to be difficult, painful, and probably economically damaging, at least in the short term.

UPDATED: July 26, 2 am. More on the ins and outs from a good basic news article in the San Diego Union-Tribune.

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