Global Warming and Hurricanes
I haven't read anything suggesting that we are having a greater number of tropical waves because of global warming. The frequency of tropical waves is cyclical and we are in a period of more frequent storms after nearly two decades of calm.
Global warming affects the surface temperature of the oceans, and while a single degree of increase may not seem like much, it has been sufficient to turn more of those waves into depressions, more depressions into storms, more storms into hurricanes, and more hurricanes are becoming major hurricanes. There is more energy available. It is the intensity of the storms that has increased.
Four of the eight most expensive storms in US records hit Florida last year.
Andrew, in 1992, was the first named storm of the season when it hit in August. There were only six named storms that year. Katrina was the 11 named storm in August of this year, and we have had four named storms since.