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The Link Between Deadly Weather and Global Warming Is Real -- and Conservatives Can't Just Wish It Away

Does extreme weather foretell the kind of climate that global warming is bringing us? Scientists say yes.

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Jeff Trepp, of Perdue University, is the leading researcher in the field.  In 2007, he published a study which combined a a high-resolution regional climate model with a suite of global climate models. The study found “a net increase during the late 21st century in the number of days in which these severe thunderstorm environmental conditions (NDSEV) occur” with the largest increases “during the summer season, in proximity to the Gulf of Mexico and Atlantic coastal regions.”  Increases of 100 percent or more were predicted “in locations such as Atlanta, GA, and New York, NY.”  Follow-up research has strengthened the case for expecting increased tornadoes in the century ahead, but there's still a great deal of work to be done, given the uncertainties that remain. 

“The most that we can say at this point is that increases in human-induced greenhouse gasses in the atmosphere will likely lead to increases in the frequency (and intensity) of the meteorological conditions that foster severe thunderstorms,” Trapp told AlterNet. “Here, a severe thunderstorm is one that produces large hail, damaging straight-line winds, and/or tornadoes.” 

“We're limited to this conclusion on 'conditions' because our climate model simulations could not explicitly resolve thunderstorms, let alone tornadoes,” Trapp explained. “Thus, the research that we're pursing at the moment involves the use of a high-resolution (also known as "convective storm permitting) model, which is providing us information about the characteristics of individual storms, as well as how the storms form.” 

As a result, Trapp said, “This leads to the question regarding uncertainty: One of the greatest uncertainties (in addition to the basic uncertainty of the climate model) is whether or not storms will form and realize the favorable meteorological conditions.  Formation -- also known as initiation or triggering -- is often linked to weather fronts, terrain, etc., and these processes were not explicitly included in our analysis.” 

Still, for all these present limitations―similar to ones that climate researchers have overcome in the past―the picture that emerges should cause concern. “Under the climate change scenario we considered, our results did show more frequent conditions in the future for certain regions,” Trapp said. “For example, the southeast U.S. and Atlantic Coastal regions might have twice as many future days with severe thunderstorm conditions, especially during their peak season.  But again, this applies to the collective hazards of hail, wind, and tornado.” 

Confronting Doubt and Denial 

Until last month, 2008 stood out as a tornado high-point. A study headed by Trapp's Purdue colleague, Noah Diffenbaugh found that “In 2008, there were 2176 preliminary tornado reports logged through mid-December, with 1600 'actual counts' (duplicate reports removed) through September, the highest total in the past half century." But April saw over 600 tornadoes, compared to an average of 160 for the month over the past decade, according to the National Oceanic and Atmospheric Administration (NOAA). The previous one-month record was 542, in May 2003.  

But a NOAA meteorologist figured prominently in a Fox News story that rightwing climate change denialists used to attack global warming activists:  

Greg Carbin, the warning coordination meteorologist at NOAA’s Storm Prediction Center in Norman, Oklahoma, said warming trends do create more of the fuel that tornadoes require, such as moisture, but that they also deprive tornadoes of another essential ingredient: wind shear. 

“We know we have a warming going on,” Carbin told Fox News in an interview Thursday, but added: “There really is no scientific consensus or connection [between global warming and tornadic activity]….Jumping from a large-scale event like global warming to relatively small-scale events like tornadoes is a huge leap across a variety of scales.” 

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