A new cycle of tropical ocean warming — a "subset" of climate troublemaker El Niño — could be key to predicting hurricanes that batter the USA, according to a study based on data that go back to the 1880s.
Researchers reported their findings in a recent issue of the journal Science.
El Niño is a periodic warming of the Pacific Ocean that usually leads to a quieter storm season. This new mode of El Niño, however, appears to cause more Atlantic tropical storms and hurricanes.
"This new type is resulting in a greater number of hurricanes with greater frequency and more potential to make landfall," says study co-author Peter Webster of Georgia Tech's School of Earth and Atmospheric Sciences.
The heart of the traditional El Niño warming occurs in the Eastern Pacific, very close to the South American coast; the recently discovered El Niño occurs thousands of miles to the west in the central Pacific Ocean, near the International Date Line.
Scientists aren't sure whether the cycle is natural or man-made: "It's difficult to differentiate between natural signals and global warming," Webster says. The frequency of the central Pacific warming does appear to be increasing, especially since 1990.
Georgia Tech scientists are tentatively calling the new phenomenon "El Niño Modoki." The Japanese word "modoki" refers to something that is "similar but different."
Unlike El Niños, which are difficult to predict before June, the central Pacific warming appears to be predictable much earlier in the year. "This could mean that we get greater warning of hurricanes, probably by a number of months," Webster says.
That also would be good news for insurers: By the time an El Niño is underway in June, the insurance industry has locked in its annual rates for the hurricane season.
"This opens up a whole new area of research," says Greg Holland of the National Center for Atmospheric Research in Boulder, Colo., who was not part of the study but did write an accompanying commentary in Science. "Separating these two warm modes may thus lead to a useful improvement in seasonal Atlantic tropical cyclone prediction," he wrote.
As for this year, "it looks like it might be a hybrid," Webster told the Associated Press, with warming starting in the east and then moving west, possibly meaning more hurricanes late in the season.
Government climate forecasters announced last week that a traditional El Niño has formed in the Pacific, which should lead to damaging winter storms in California and increased storminess across the southern USA.
In May, the National Oceanographic and Atmospheric Administration predicted that there would be nine to 14 named storms in the Atlantic this year, of which four to seven could become hurricanes, including one to three major hurricanes (category 3, 4 or 5).
Research into El Niño Modoki is still too new to change the official forecast for this year. In the future, hurricane forecasters may be able to incorporate the data into their seasonal predictions.
The study was led by Webster, Hye-Mi Kim and Judith Curry, all of Georgia Tech. The team used satellite data along with historical tropical storm records and climate models in their research.
Contributing: The Associated Press