Global Warming and Twisters.

A new report from Columbia University researchers adds no new evidence to show climate change (i.e. global warming") is at fault, but it doesn't dismiss it either.

“Something’s up,” (researcher) Tippett said. “The tornadoes that do occur are occurring in clusters. It’s not any increase in the (total) number of tornadoes.”
Marsh said until Tuesday’s outbreak, (11-29-16) there had been 830 tornadoes all year , which was below the previous low for that date of 920. The normal number through late November is closer to 1,300. While 2011 was one of the busiest tornado years for the size of twisters that Tippett studied, 2012 was one of the quietest, he said.