Warming Could Mean More Hawaii Hurricanes

For the second summer in a row, a tropical cyclone is headed toward Hawaii, a relative rarity for the island chain.  But in a warming world, the 50th state could face more tropical storms and hurricanes, some research suggests, with one new study finding that climate change upped the odds of last year’s spate of storms.

Though Hawaii is a tropical island, it doesn’t have the same risk of being hit by tropical cyclones (the generic term for tropical storms, hurricanes and typhoons) that islands in the Caribbean or Asia have.  That’s because it is typically surrounded by relatively cold ocean waters and is in a region with wind patterns that tend to produce a lot of what is called shear, or a difference in the speed or direction of winds at different heights in the atmosphere that tend to rip apart a storm.

But this summer and last, that natural protection has been diminished.  An El Niño has reversed those upper level winds and reduced some of the shear that can break up storms. Storms also tend to form further to the west in the eastern Pacific during El Niño years, which makes it more likely they could reach Hawaii.  The relationship between a higher hurricane risk for Hawaii and El Niño has been well established.

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One of the big research topics in climate change has been how warming might affect the occurrence and intensity of tropical cyclones in different parts of the world.  In a study to be published in the Bulletin of the American Meteorological Society in September, researchers looked at how it might be linked to last year’s flurry of Hawaiian hurricane activity.

Using computer simulations, they found that “the extremely active 2014 Hawaiian hurricane season was made substantially more likely by anthropogenic forcing,” they wrote in the study, as that forcing has changed weather patterns in the atmosphere.  They stressed, though, that natural variability, including the El Niño cycle, also played an important role.

Two other researchers who look at the influence of climate change on hurricanes, Suzana Camargo of Columbia University, and Kerry Emanuel of MIT — neither of whom was involved in the new study — said that the study’s findings seemed sound and was in line with other recent research.  Emanuel said that a study he did in 2013 that used climate models from the latest iteration of the Intergovernmental Panel on Climate Change report also pointed to an increase in the frequency of hurricanes around Hawaii.

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