Saturday, September 1st 2012, 11:55 AM EDT
The U.S. just can’t seem to buy a major hurricane. It’s been 2,535 days since the last Category 3 storm, Wilma in 2005, hit the beach. That’s the longest period—by far—in the record that goes back to 1900.
Consequently, the global warming hype machine is being reduced to running on Category 1 fumes. Hence last August’s Irene (which was barely a hurricane) and the recent Isaac (with a much more respectable wind field) became the sorry excuses used to hector the public into demanding massive energy taxes.
But didn’t last year’s Irene drop a huge amount of rain, a sure sign of its ingestion of the global warming steroid? Not really. While that argument makes the alarmist blogs and MSNBC, it neglects that, everything else being equal, if hurricanes are becoming rainier, they must be getting stronger, as the fuel that drives the kinetic whirl of the tropical cyclone is the heat released by the condensation of water. Comprehensive global analyses of tropical cyclone strength show no change.
Aren’t there more whoppers—the powerful Category 4 and 5 monsters that will mow down pretty much anything in their path? As is the case with much severe weather, we simply see more than we did prior to satellites and (in the case of hurricanes) long-range aircraft reconnaissance. As the National Hurricane Center’s Chris Landsea (with whom I have published on tropical cyclones) has shown, if you assume the technology before satellites, the number of big storms that would be detected now is simply unchanged from the past.
There’s a pretty good example of this spinning in the remote Atlantic right now, which is Hurricane Kirk, far away from shipping channels, land, and nosy airplanes. Kirk is compact enough that it would likely have been completely missed fifty years ago. If it spins up into a Category 4 (which is currently not forecast), that would be another biggie that would have gotten away, back in the day.
There’s another reason that the increase in frequency is more apparent than real: “shorties”. That’s what Landsea calls the ephemeral tropical whirls of little consequence that are now named as storms more because of our detection technology than anything else. There’s also probably an overlay of institutional risk aversion in play, as it is now recognized that seemingly harmless thunderstorm clusters over the ocean can spawn decent floods when they hit land.
There is another driver for an increase in Atlantic hurricane frequency that isn’t operating elsewhere. In 1995, a sudden shift in the distribution of North Atlantic temperatures increased hurricane frequency. Landsea predicted—at the time—that the Atlantic would soon fire up from its hurricane doldrums of the previous two decades, which it did. This type of shift has occurred repeatedly in the last century, both before and during (modest) global warming from greenhouse gases.
The whole notion of greater hurricane activity caused by surface warming is easily adjudicated by a look at Ryan Maue’s Accumulated Cyclone Energy (ACE) index, which he updates monthly on his site weatherbellmodels.com/weather. Maue is a refreshing sort—one of the few young scientists willing to call out global warming hype when he sees it. (Instead, most of my fellow travelers are post-middle-age people who can afford to squawk, even if that makes it very difficult to publish papers.)
The top blue plot is the global accumulated kinetic energy from all tropical cyclones (tropical storms and hurricanes), the bottom black plot is for the Northern Hemisphere, and the red line is the global surface temperature anomaly from the Climate Research Unit at the University of East Anglia. All figures are presented as 24 month running sums. It is obvious that any relationship broke down as earth’s temperature reached a plateau.
A comparison of Maue’s historical record and surface temperatures is what scientists call a test of hypothesis—in this case, the notion that global hurricane activity is increasing because of warming. The failure is obvious: as warming peaked and plateaued, ACE dropped to some of its lowest levels measured.
It’s time to stop conflating the latest Category 1 swirl with climate change. And, yes, it is also high time for a very powerful storm to finally land on some unfortunate beachfront community, which will no doubt portend the end of the world as we know it.