Is global warming a factor behind the deadly tornadoes?

At least 50 people were killed in fierce storms that struck across the South yesterday. Tennessee appears to have been hardest hit, with more than two dozen deaths reported so far -- including 10 in Macon County alone. Arkansas, Alabama and Kentucky have also reported fatalities.

The storms came amid unusually warm weather across the Southeast, with record-setting temperatures recorded yesterday in Tennessee, North Carolina and Virginia. As the BBC reports:

The tornadoes were unusual in that they do not typically hit during the winter. However this is the second time this winter in which deadly tornadoes have struck the US, the first being early in January. The storms were caused by the meeting of a cold front with warm, moist air which has covered the southern states over the last few days. One scientific study into global warming is predicting that tornadoes and thunderstorms will increase in intensity and frequency.