The number of major Atlantic storms has increased over the past 100 years, in concert with the rise in ocean temperatures. Contradicting some past conclusions, a study in Nature Geoscience predicts that as the world heats up, the number of hurricanes will decrease, although the storms will produce more rain. Rather than being driven by warmer waters per se, the 20th-century rise may have stemmed from temperature differences between the tropical Atlantic and other basins, which have not warmed as quickly. As sea-surface temperatures of the other basins catch up, storm frequency may decline.

Average number of hurricanes from:

1905 to 1930: 3.48

1931 to 1994: 5.08

1995 to 2005: 8.44

Rise in tropical Atlantic sea-surface temperature since 1900: 0.7 degree Celsius Projected rise by 2100: 1.7 degrees C

Projected drop by 2100 in:
Tropical storms: 27 percent

Hurricanes, Category 1 and 2: 18 percent

Hurricanes, Category 3, 4 and 5: 8 percent

SOURCES: Nature Geoscience, June 2008; National Oceanic and Atmospheric Administration; Philosophical Transactions of the Royal Society A, November 15, 2007 (historical data)