What we can say with some certainty is that the number of years with very large tornado losses has actually decreased. Consider that from 1950 to 1970 the U.S. saw 15 years with tornado damage in excess of $5 billion a year. From 1993 to 2013 there were only four such years, with three since 2008.Read the whole thing here. The peer-reviewed paper (cited by IPCC AR5) and data on which the op-ed is based can be found here.