Fossil fuels linked to increase in hurricanes: 19 scientists point to global warming

ATLANTA - Human-induced climate change is the driving force behind higher ocean temperatures in hurricane spawning regions, scientists from eight major research institutions reported Monday.

The findings, published in the Proceedings of the National Academy of Sciences, provide the strongest evidence yet that man-made greenhouse gases are playing a major role in the increase in both the number and intensity of hurricanes.

"There is now substantial evidence that human-caused changes in greenhouse gases are the main driver of sea surface temperature in hurricane forming regions of the Atlantic and the Pacific," said Thomas Wigley, senior scientist at the National Center for Atmospheric Research.

Greenhouse gases, primarily carbon dioxide and methane, are emitted by factories, power plants, automobiles, intensive agriculture and forest burning. Levels of such gases in the atmosphere have been increasing since the dawn of the industrial revolution.

Wigley, one of 19 co-authors of the study, said increases in hurricane activity have so far been driven by relatively small increases in tropical ocean temperatures, a degree or less over the last century. But he noted that if global warming continues as predicted, those regions will heat up faster.

The researchers acknowledge that hurricane activity -- including the record 27 named Atlantic storms and 15 hurricanes during the last season -- is a result of many factors, including natural ones.

But their analysis suggests man-made factors account for at least two-thirds of the increase in sea surface temperatures over the last century.

Skeptics remain unconvinced. Colorado State University researchers Philip Klotzbach and William Gray, who have issued annual estimates of hurricane activity for more than 20 years, contend that recent hyperactive hurricane seasons are part of a decades-long cycle. "No credible observational evidence is currently available that directly associates global surface temperature change with changes in hurricane frequency or intensity," Klotzbach said.

Benjamin Santer of the Lawrence Livermore National Laboratory said he and his fellow researchers ran more than 80 simulations on 22 computer models developed around the world.

The results, he said, show it is "virtually impossible" to explain what has been happening solely as a result of natural variation in climate, volcanic eruptions, or changes in solar radiation.