El Nino And African Monsoon Have Strongly Influenced Intense Hurricane Frequency In The Past

“The processes that govern the formation, intensity, and track of Atlantic hurricanes are still poorly understood,” said Donnelly, an associate scientist in the WHOI Department of Geology and Geophysics. “Based on this work, we now think that there may be some sort of basin-wide ‘on-off switch’ for intense hurricanes.”

From ScienceDaily

And from Reuters by way of Planet Ark:

" Intense hurricanes hit when local sea surface temperatures were warm or cool. In fact, "the Caribbean experienced a relatively active interval of intense hurricanes for more than a millennium when local sea surface temperatures were on average cooler than modern," the study said."