Wednesday, August 31, 2011

Hurricane Hype

Was Hurricane Irene God's way of telling New Yorkers that gay marriage was a bad idea (by killing people mostly in North Carolina, etc)?  Maybe, but wouldn't it have been more efficient for him to just get a twitter account?  Or go on the Sunday talk show circuit?

What a significant landfalling hurricane always is is a good publicity opportunity, so those with a climate axe to grind are as quick to jump on that boat as fundamentalist ministers and rabbis.  Bill Mckibben blamed Irene's (as it turned out, overestimated) strength on global warming.  Planet denial was quick to respond.  James Taylor, writing in Forbes, claimed that there has been a 100 year plus trend of decrease in landfalls of Atlantic hurricanes on the US.

The facts are a bit more ambivalent.  NOAA's 150 year history of US landfalling hurricanes  shows a weak trend of decrease over time.

US landfalling hurricanes are only a very small percentage of global landfalling hurricanes of course, so I don't take this too seriously as a global indicator, and of course the older data may be more problematic.

From the standpoint of atmospheric physics, global warming could affect hurricane frequency in a few ways: warmer sea surfaces, changing wind shear, and lofted dust to name three.   These tend to be countervailing, and so far as I know, there is no solid evidence that global warming has affected hurricane frequency in any systematic way.

Hurricane intensity is affected by the same factors (among others) but is probably more sensitive to sea surface temperature.  Last time I checked, there was evidence, albeit somewhat controversial, that the number of intense hurricanes is increasing.

In Irene's case, the warmer sea surface temperatures off the East coast were there to support greater intensity, but wind shear and dry air cut it down in intensity.