Is a Warming Climate Causing More Severe Weather?

Is a Warming Climate Causing More Severe Weather?

Thunderstorm activity in the last week has been extremely active. When you have thunderstorms that spawn these unusually strong tornadoes you need three conditions: cool dry air from the north converging with warm moist air from the south (primarily the Gulf of Mexico) and the jet stream which provides the wind shear. Those three conditions just converged to ramp up tornado activity. Add all these three elements and you have what we've experienced this week: a massive amounts of tornadoes rampaging across the south of the United States. These conditions are not unusual except for the intensity. We should expect to see more frequent and more intense thunderstorms spawning more intense tornadoes as the atmosphere heats up and retains more moisture.So, I will repeat the question.

Is a Warming Climate Causing More Severe Weather?

A noted scientist recently gave a speech saying that he wasn't sure if global warming and climate change were responsible for the recent string of tornadoes. That seems to fly in the face of the physics involved. The last year was notable, and so far the number of tornadoes was actually fewer but when they occurred the intensity was greater. Witness Joplin Missouri, Tuscaloosa Alabama, and Birmingham Alabama in 2013. Extremely violent tornadoes destroyed buildings, leveling neighborhoods and creating chaos in a lot of damage these could be attributed to the fact that there's more housing density in the suburbs.

There are well established methods for measuring the strength of tornadoes, the Enhanced Fujita Scale, which estimates wind speeds from damage on the ground. This method shows clearly that the long term trend of stronger tornadoes has been decreasing since reliable records started to be kept around 1970.

James Elsner at Florida State University has a killer curve. The curve indicates that tornadoes in the U.S. may be getting stronger. “If I were a betting man I’d say tornadoes are getting stronger,” he noted on Tuesday during a lecture at the annual American Geophysical Union fall meeting in San Francisco.

   Elsner showed his final graph, adding up the kinetic energy of tornadoes each year from 1994 to 2012. The curve is flat from 1994 to about 2006 but then spikes upward through 2012. It was reminiscent of the now famous “hockey stick” graph produced by Michael Mann and colleagues a decade ago. Elsner has 20 years of data. His data begin in 1994 because that’s when Doppler radar started tracking tornadoes across the U.S. The curve shows the length and width of a tornado’s damage path and gives an accurate indication of the storm’s peak wind speed. It is difficult to measure that directly as it is done for hurricanes by ground instruments and planes that fly into the storms.