no blood on our hands, then

Many people operate under the eminently reasonable theory that global warming is part and parcel of warming oceans, including of course the Gulf of Mexico, which in turn amps up the intensity and duration of hurricanes. I’ve stated as much here. Real Climate takes a very exacting scientific approach here.

Ross Gelbspan said simply: “The hurricane that struck Louisiana yesterday was nicknamed Katrina by the National Weather Service. Its real name is global warming.”

This strikes some as an accusation –- an accusation they feel they can safely deride and ignore. Now, while it is certain at this point that the globe is warming, long time deniers with ties to the elephantine side of the U.S. government attempt to cover their shame and retain personal dignity by claiming that humans have nothing to do with global warming –- these are natural cycles.

Consider the arguments of James Glassman, attempting to rebut Ross Gelbspan and others:
(T)he response of environmental extremists fills me with what only can be called disgust. They have decided to exploit the death and devastation to win support for the failed Kyoto Protocol, which requires massive cutbacks in energy use to reduce, by a few tenths of a degree, surface warming projected 100 years from now.

Katrina has nothing to do with global warming. Nothing. It has everything to do with the immense forces of nature that have been unleashed many, many times before...

The hyperbolic paragraph regarding the limpidly feckless Kyoto treaty is so far outside the bounds of observable reality that no specific rebuttal is required. As to Katrina having nothing to do with global warming, that is not established. Given a warming globe, and localized warming in the Gulf, the intensity of this specific storm appears to have been raised. One has to wonder how NOAA was able to predict that this hurricane season would be unusually intense. Tea leaves, perhaps, or goat entrails.

It is logically correct to say that “(Katrina) has everything to do with the immense forces of nature that have been unleashed many, many times before”. It follows that a category five hurricane might well have struck New Orleans in the absence of global warming.

It does not follow that the presence of global warming fails to affect hurricanes in general, including Katrina, and that the scope and devastation of hurricanes and other weather events is likely to become more extreme, as has long been predicted by climatologists. See “The Change in the Weather” for a good survey of this topic.

Giant hurricanes are rare, but they are not new. And they are not increasing. To the contrary. Just go to the website of the National Hurricane Center and check out a table that lists hurricanes by category and decade. The peak for major hurricanes (categories 3,4,5) came in the decades of the 1930s, 1940s and 1950s.

Ok I will check the website, and I suggest you do as well. Fascinating. Glassman says that major hurricanes have “peaked”, as if hurricane were a natural resource like oil that one could deplete. However: Organized as it is in decades, note that the last decade on the chart is incomplete –- filled out through 2004! Add in 2005 major hurricanes -- two so far and we are in the middle of the season. Extrapolate obvious weather trends through 2010. The “peak decade” is in danger of being surpassed.

"Because hurricanes form over warm ocean water, it is easy to assume that the recent rise in their number and ferocity is because of global warming. But that is not the case, scientists say. Instead, the severity of hurricane seasons changes with cycles of temperatures of several decades in the Atlantic Ocean. The recent onslaught 'is very much natural,' said William M. Gray, a professor of atmospheric science at Colorado State University who issues forecasts for the hurricane season.'"

Gray is a climate contrarian, and skepticism is a fine thing in science. Hurricanes are a great way for skeptics to get a little footing on the topic, because hurricane data is not complete going back through the decades –- compare the complete satellite coverage of the present era. I’m sure spotty and incomplete data from the 1940’s etcetera leads to some corker arguments for scientists, even amongst global warming proponents.

Meanwhile, the glaciers are melting and the tundra is defrosting.
Global warming affects the temperature of the oceans, which in turn affects hurricanes.

Katrina was a hurricane.