El Nino, the periodic eastern Pacific phenomenon credited with shielding the US and Caribbean from severe hurricane seasons, may be overshadowed by its brother in the central Pacific due to global warming, research has indicated.
"There are two El Ninos, or flavors of El Nino," said Ben Kirtman, co-author of the study and professor of meteorology and physical oceanography at the University of Miami's Rosentstiel School of Marine and Atmospheric Science.
"In addition to the eastern Pacific El Nino which we know and love, a second El Nino in the central Pacific is on the increase," he added.
The eastern El Nino increases wind sheer in the Atlantic that may hamper the development of major hurricanes there.
The central Pacific El Nino, near the International Dateline, has been blamed for worsening drought conditions in Australia and India as well as minimizing the effects of its beneficial brother to the east.
Led by Sang-Wook Yeh of the Korea Ocean Research and Development Institute, a team of scientists applied Pacific Ocean sea surface temperature data from the past 150 years to 11 global warming models developed by the Intergovernmental Panel on Climate Change.
Eight of the models showed that global warming conditions will increase the incidence of the central Pacific El Nino.
Over the past 20 years, according to the data, the frequency of an El Nino event in the central Pacific has increased from one out of every five to half of all El Nino occurrences.
"The results described in this paper indicate that the global impacts of El Nino may significantly change as the climate warms," said Yeh.
An increase in central Pacific El Nino events may reduce the hurricane-shielding effects of the eastern Pacific event.
"Currently, we are in the middle of a developing eastern Pacific El Nino event, which is part of why we're experiencing such a mild hurricane season in the Atlantic," said Kirtman.
"We also anticipate the southern United States to have a fairly wet winter, and the northeast may be dry and warm," he added.
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 Atlantic hurricane season in 2010.