September 28, 2009

Global warming may cause more hurricanes

Scientists say the eastern Pacific El Nino, which can shield the United States from severe hurricane seasons, may be reduced in effectiveness by global warming.

There are two El Ninos, or flavors of El Nino, said Ben Kirtman, a professor at the University of Miami's Rosentstiel School of Marine and Atmospheric Science. In addition to the eastern Pacific El Nino "¦ a second El Nino in the central Pacific is on the increase.

El Nino is a recurring warm water current along the equator in the Pacific Ocean. Meteorologists say the eastern El Nino increases Atlantic wind sheer, hampering hurricane development. The central Pacific El Nino has been blamed for worsening drought conditions in Australia and India, as well as minimizing the effects of the eastern El Nino.

The scientists, led by Sang-Wook Yeh of the Korea Ocean Research & Development Institute, applied Pacific Ocean sea surface temperature data from the past 150 years to 11 global warming models.

Yeh said the study suggests the global impacts of El Nino may significantly change as the climate warms.

Currently, we are in the middle of a developing eastern Pacific El Nino event, said Kirtman, which is part of why we're experiencing such a mild hurricane season in the Atlantic.

Kirtman expects the current El Nino event to end next spring, perhaps followed by a La Nina, which he expects may bode for a more intense 2010 Atlantic hurricane season.

The study appears in the journal Nature.