NCPA - National Center for Policy Analysis


October 5, 2005

Environmental lobbyists quickly responded to the Gulf Coast devastation of hurricanes Katrina and Rita with loud assertions that the underlying cause of these more frequent, more dangerous and more costly hurricanes is global warming caused by human greenhouse gas emissions. There is just one problem: science. Historical data and ongoing hurricane research reveal scant evidence linking human-caused warming to more frequent or powerful hurricanes, says H. Sterling Burnett, a senior fellow with the National Center for Policy Analysis.

Physics of Hurricanes:

  • Hurricanes only form at sea surface temperatures above 80 degrees F, and ocean temperatures have increased modestly over the past 50 years.
  • But ocean temperatures are only one factor in the formation, power and longevity of hurricanes.
  • Hurricanes are heat engines and their longevity and severity are partly driven by temperature differences between the ocean water and the air temperature; the smaller the difference, the less severe the storm.
  • Even if global warming modestly increases ocean temperatures in the coming century, the gap between ocean and air temperatures will shrink because there will be little or no increase in air temperatures nearest the equator, where hurricanes form.

According to scientists at the National Oceanic and Atmospheric Administration (NOAA), because the changes in both factors are likely to be small, neither the increased ocean temperatures nor the reduced differential between the air and water temperatures are likely to result in any changes in hurricane frequency or intensity.

At the 27th Annual National Hurricane Conference, University of Colorado atmospheric scientist Dr. William Gray explained that natural, periodically changing ocean circulation patterns, not humans, are responsible for hurricane cycles. This, he said, includes the current worldwide cycle of increasing hurricane activity.

Source: H. Sterling Burnett, "Hot Air vs. the Cold Hard Truth about Hurricanes and Global Warming," National Center for Policy Analysis, Brief Analysis No. 530, October 5, 2005.

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