Contrary to many previous reports, global warming could reduce the number of hurricanes that strike the United States, according to a new study.
The work is the latest in a contentious scientific debate over how human-induced global warming might affect the intensity and frequency of hurricanes.
In the study, researchers from the National Oceanic and Atmospheric Administration and the University of Miami in Florida link warming oceans to increased vertical wind shear in the Atlantic Ocean near the United States.
Wind shear—a change in upper-level wind speed or direction—makes it hard for hurricanes to form, strengthen, and stay active.
With every degree Celsius that the oceans warm, the wind shear increases by up to 10 miles (16 kilometers) an hour, said lead study author Chunzai Wang, a physical oceanographer at NOAA.
So that means "global warming may decrease the likelihood of hurricanes making landfall in the United States," according to the study authors.
The NOAA findings support results released last April in which a suit of climate models also predicted an increase in wind shear due to warming.
The new study is based on observations instead of computer models, Wang noted.
Observations made between 1854 to 2006 show that sea-surface temperatures are rising globally, his team says, with significant warming in the tropical regions of the Pacific, Atlantic, and Indian oceans.
Ocean temperatures in the tropical Pacific and Indian oceans have global effects, much like the Pacific weather phenomenon known as El Niño does, Wang said.
Warming in those regions will increase wind shear in the areas of the Atlantic where hurricanes form.
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