Ron Bailey takes a well-Reason-ed approach.
“So as Americans become wealthier, tornado damage may get worse. On the other hand, casualties will likely fall, as technological advances increase warning times, enabling people to get out of way or take shelter sooner. Sen. Boxer is right about this much: Tornados are a kind of extreme weather. But on the evidence so far, she is wrong to suggest that the Moore tornado is related to climate change.”
The answer to the headline, No, or probably no.
Actually, F5 tornadoes have decreased dramatically in number according to: http://www.spc.noaa.gov/faq/tornado/f5torns.html
But why let facts get in the way?