From the ABC 7 Weather team

Is climate change creating more 100° degree days in D.C.? (MAP)

July 29, 2011 - 12:53 PM
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It's a stifling 102 degrees at Reagan National, a new record. In the future, should D.C. get used to a higher number of 100-degree days?

A sticky, white-hot thermometer over at Reagan National just hit 102 degrees. That reading slaughtered the old 1993 record high of 99 degrees. The rising heat has also beat the 97-degree record at Dulles and is sliding up to knock over the 99-degree record at BWI. Going outside feels like sticking your head into an oven.

Should we get used to it?

Yes indeedy, say scientists from the U.S. government, Cambridge University and elsewhere. They've compiled a few illustrative, sweat-inducing maps showing two different scenarios in the near future, depending on how much we control greenhouse gases. (The maps are included the 2009 report, Global Climate Change Impacts in the United States.) First, take a look at the number of days from 1961 to 1979 where the heat surpassed 100 degrees:

100 degree days in United States historical

Slices of California, the Southwest and the Southern Plains in Texas and Oklahoma had several weeks of above-100-degree days. Everybody else, including the District, was lucky to get 10 days where the heat maxed out above 100, and many states didn't get any. Nice. Now let's see what could happen as the climate timeline begins to split.

In Scenario No. 1, humanity does a pretty good job of reducing greenhouse gas emissions. It will still be way hotter in the U.S., but not quite as bad as it could be. By 2080 to 2099, here's how many regions could experience skin-peeling heat:

100 degree days in United States future

Southern California and Arizona receive more than 90 days a year where temperatures break through the 100 ceiling, and states that used to be chill and bearable, like Washington and Montana, all of a sudden have 10 to 20 of these miserable days.

What if humanity decides to do nothing to mitigate emissions? Well, the climatologists behind this report see a United States locked in an eternal heat wave where everybody walks around panting and spouting tired "Hot enough for ya?" quips before passing out on griddlelike sidewalks and cooking to medium-doneness (presumably). Texas could suffer 100 or more days of the year where temperatures beat 100 degrees and the East Coast now receives a drubbing of more than 30 days above 100:

100 degree days in United States future

To put this in perspective, D.C. has only had 4 days this year where we were above 100, and to many it already feels like an endless summer. But simple discomfort is just the tip of the volcano. In a hotter world, say the folks behind this report:

The increase in extremely hot days would put an aging U.S. population at the risk of illness and death. Greater demand for air conditioning may also trigger more summer electricity blackouts, and the heat will make it more difficult to keep urban air pollution, including ground-level ozone, at healthy levels.

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