Hurricanes and Hot Air
By WILLIAM M. GRAY
July 26, 2007; Page A12
Though the 2007 hurricane season is off to a slow start, my colleague Phil Klotzbach and I will be updating our seasonal Atlantic Basin Hurricane Activity Forecast on Aug 3. We still anticipate another active season — an above-average number of major hurricanes with maximum sustained winds in excess of 110mph.
Since 1995, the Atlantic basin has experienced a significant increase in major hurricanes, with 47 major storms in the last 12 years. During the prior 25-year period, 1970 to 1994, there were only 38 major hurricanes, or, on an annual basis, slightly less than 40% as many. On a long period normalized basis, major hurricanes account for about 80% to 85% of all
Some scientists, journalists and activists see a direct link between the post-1995 upswing in
Atlantic hurricanes and global warming brought on by human-induced greenhouse gas increases.
This belief, however, is unsupported by long-term
Consider, for example, the intensity of
that the periods must be long enough to reveal long-term trends. During the most recent 50-year
period, 1957 to 2006, 83 hurricanes hit the
The hypothesis that increasing carbon dioxide in the atmosphere increases the number of hurricanes fails by an even wider margin when we compare two other multi-decade periods:
1925-1965 and 1966-2006. In the 41 years from 1925-1965, there were 39
If global warming isn’t the cause of the increased Atlantic hurricane activity seen over the past dozen years, what is?
Here’s how it works. Though most people don’t realize it, the
The strength of the
THC is weaker than average.
Since 1995, the
A number of my colleagues and I have discussed the physics of Atlantic THC variations in our seasonal hurricane forecasts and in various conference talks for many years. Those who are convinced that greenhouse gas increases provide the only plausible explanation for the recent increases in hurricane activity are either unaware of our work, or don’t want to consider any alternative.
One reason may be that the advocates of warming tend to be climate modelers with little observational experience. Many of the modelers are not fully aware of how the real atmosphere and ocean function. They rely more on theory than on observation.
The warming theorists — most of whom, no doubt, earnestly believe that human activity has triggered nature’s wrath — have the ears of the news media. But there is another plausible explanation, supported by decades of physical observation. The spate of recent destructive hurricanes may have little or nothing to do with greenhouse gases and climate change, and everything to do with the
Mr. Gray, professor emeritus in the Department of Atmospheric Science at Colorado State
University and a research fellow at the Independent Institute has been issuing Atlantic basin seasonal hurricane forecasts for the past 24 years.