Global warming: a major factor in Rita and Katrina?

By Robert Bazell for NBC News:

In recorded history, two storms as powerful as Hurricanes Rita and Katrina have never hit the United States in one season. A coincidence, perhaps, but scientists say ocean temperature could be big factor...

Scientists say one season, even like this one, cannot indicate anything about climate change. But those same measurements show that in the past 50 years the oceans have gotten one degree warmer. That may not sound like much, but the experts say it is a lot of energy.

Indeed, recent studies show that, worldwide, the number of Category 4 and 5 hurricanes has doubled with that one degree change and that’s a source of worry. “At the moment we’ve only warmed up one,” says Dr. Stephen Schnieder, a climatologist at Stanford’s Institute for International Studies. “What happens when we warm up three or five degrees — which is projected in the next several decades to the end of the century?”