Dr. Chuck Doswell nails it (as usual):
But in the case of tornadoes, a few climate scientists (e.g., Dr. Trenberth) are overstepping their domains of expertise. If I give them the respect that their work is due in an area within which I have no record of peer-reviewed publications, I would expect them to do likewise regarding the work I (and my colleagues) have done in an area wherein these climate scientists have no record of peer-reviewed publications. I don’t speculate about global climate change, so I have every reason to expect them not to engage in unfounded speculation about tornado occurrence frequency.
(via: Patrick Marsh)