The death toll from last week’s devastating tornadoes in the Midwest and South has reached 39. The storms caused damage across Alabama, Georgia, Indiana, Kentucky and Ohio. Meteorologists say this year’s mild winter has increased the chances for severe weather across much of the United States. In 2007, NASA’s Goddard Institute on Climate Science issued a report predicting larger and more violent thunderstorms and tornadoes in the United States as global warming trends continue.