Whistling in the wind

Seeing the 'black swans' among the storms is a tricky business.

Forecasters from the US National Oceanic and Atmospheric Administration are predicting that the 2008 Atlantic hurricane season beginning Sunday and ending November 30 will be more tempestuous than usual. The agency has predicted a 65% probability of an above-average season, a 25% chance of a near-normal season, and a 60% to 70% chance that there will be two to five major hurricanes. An average season has 11 named storms, including six hurricanes for which two reach major status.

Yet the same agency has also predicted that the number of hurricanes and tropical storms forming over the Atlantic may drop this century because of global warming, which contradicts theories that climate change will boost storminess. The scientists took a climate model that mirrors the increase in Atlantic storms in recent years, and then plugged in forecasts for future warming. The results, published in Nature Geoscience, showed a decline in the numbers of both hurricanes and tropical storms.

The New Scientist writes that the findings have discombobulated hurricane theory, stating that hurricanes form over the oceans when sea surface temperatures exceed about 26 degrees. "Now things are not so clear.  That 26 degree rule assumes other things are equal, and they never are."