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Poisoned Weather: Global Warming Helped Fuel Killer Tornadoes

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"Poisoned Weather: Global Warming Helped Fuel Killer Tornadoes"

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Unusually hot Gulf of Mexico surface temperatures, March 5, 2012

Carbon pollution from fossil fuels is poisoning the weather, helping drive the conditions that created the killer tornado outbreak last week across the heart of the United States. More than 85 tornadoes killed at least 38 people and devastated communities in ten states. The furious storms formed as a strong cold front from the north crashed into high humidity and warm temperatures from the south.

Meteorologist Jeff Masters explained to USA Today that the warm, humid air that fed the tornadoes comes from an unusually hot Gulf of Mexico:

“This year’s unusually mild winter has led to ocean temperatures across the Gulf of Mexico that are approximately 1 degrees C (1.8 degrees F) above average,” says meteorologist Jeff Masters of the Weather Underground. This places it among the top ten warmest values on record for this time of year, going back to the 1800s, he says. “Friday’s tornado outbreak was fueled, in part, by unusually warm, moist air flowing north from the Gulf of Mexico due to the high water temperatures there,” Masters says. He says this exceptionally warm air set record high temperatures Friday afternoon at 28 airports in Louisiana, Arkansas, Mississippi, Alabama, Tennessee, Kentucky, and Georgia. Warmer winters — and an earlier arrival of spring due to a warming climate — will allow tornado season to start earlier and end earlier. “This year’s early start to tornado season is consistent with what we would expect from a warming climate.”

“Baseline ocean temperatures have indeed warmed because of global warming,” Masters told ThinkProgress Green in a follow-up, “so part of the hot Gulf of Mexico temperatures can be blamed on global warming.”

It is irresponsible not to mention climate change,” climatologist Kevin Trenberth of the National Center for Atmospheric Research told ThinkProgress Green last year. “The environment in which all of these storms and the tornadoes are occurring has changed from human influences (global warming).”

“As spring moves up a week or two, tornado season will start in February instead of waiting for April,” Trenberth told Reuters this week. The winter season from December to February was the fourth warmest on record for the lower 48 states, according to the National Oceanic and Atmospheric Administration (NOAA).

“Inherently the global warming from humans is quite small from one year to the next, but 10 times larger from one decade to next, and so on,” Dr. Kevin Trenberth told ThinkProgress Green in an email interview. With over a hundred years of man-made global warming from the start of the Industrial Revolution, the cumulative effect of greenhouse pollution has become significant enough to change ocean temperatures and regional weather patterns in measurable ways. “But superposed is all the shorter term natural variability that at any time can offset that or amplify it,” Trenberth cautioned.

Because of that variability and imperfect historical records, scientists have not found a measurable trend in tornado intensity and number. However, with greater greenhouse pollution scientists expect changes. “The number of days when conditions exist to form tornadoes is expected to increase” as the world warms, atmospheric scientist Robert Trapp told Reuters.

Scientists are only beginning to have a formal understanding of how our disruption of the global climate is influencing extreme weather such as tornado-bearing thunderstorms. However, a picture is beginning to emerge, NASA climate scientist Anthony D. Del Genio wrote in 2011: “As the climate warms, we might experience fewer storms overall, but more of the strongest storms.” They have identified the risk of longer tornado seasons with stronger thunderstorms. Meanwhile, right-wing austerity policies are causing cutbacks in weather monitoring, infrastructure maintenance, and emergency preparedness.

In the face of this warning, we must ask if our current path of increased pollution and decreased investment in public safety is the wisest course.

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