Hurricanes are getting stronger, but why?

Research finds that hurricanes have been getting stronger in recent decades. Scientific American reports:

According to an analysis published today in Science, the number of Category 4 and Category 5 hurricanes has almost doubled in the past 35 years...

"In the 1970s, there was an average of about 10 Category 4 and 5 storms hurricanes per year globally," Webster notes. "Since 1990, the number of Category 4 and 5 hurricanes has almost doubled, averaging 18 per year globally."

Link

But can we blame this trend on "global warming"? It seems that the jury is still out:

Dr Peter Webster [the same guy that headed the previously noted study], believes there may be a link to climate change.

'What I think we can say is that the increase in intensity is probably accounted for by the increase in sea-surface temperature,' he told the BBC News website, 'and I think probably the sea-surface temperature increase is a manifestation of global warming.'

'The problem is,' observes Julian Heming, 'that we can only look back about 35 years with satellite data; before that the record is somewhat unreliable, and 35 years isn't long enough to draw a definite conclusion.

Link (emphasis added)