Hurricanes may become more common in northeastern US, bringing new risk to major cities
Summary
New research indicates that storms once limited mostly to tropical regions will affect broader swath of the globe
When Hurricane Sandy made landfall near New York City almost a decade ago, bringing huge storm surges and 7 inches of rain that caused widespread flooding and blackouts, the superstorm was seen as an exceedingly rare event. Though common in regions closer to the equator, including the Caribbean and along the Gulf Coast, such storms rarely make direct strikes on the northeastern U.S.
But a new study suggests that as the planet warms, the storms will become more common in mid-latitude regions—between 30 and 60 degrees latitude in both hemispheres—that include New York City and Boston as well as Beijing, Tokyo and other large cities in eastern Asia and Australia.
“Places like New York, which are not in the deep tropics, have always had hurricanes, but only rarely," said Joshua Studholme, a Yale University climate physicist and the lead author of the study, published last month in the journal Nature Geoscience. “The climatology is changing and that is likely to be a shock."
An expanding hurricane range means more people as well as homes and businesses may be at risk in coastal areas, said Jim Kossin, a former National Oceanic and Atmospheric Administration scientist who wasn’t involved in the new research.
The equatorial region that gives rise to tropical cyclones—known as hurricanes in the Atlantic and typhoons in the western Pacific—will likely expand toward both poles as meteorological conditions conducive to tropical-cyclone formation there become more common.
“Even a small poleward shift in the average latitude where tropical cyclones track can cause very large changes in exposure at higher latitudes," said Dr. Kossin, who now works for The Climate Service, a climate-risk analysis company.
Hurricanes typically develop in regions where prevailing winds are light and the ocean surface temperature is above 80 degrees Fahrenheit. Such conditions are common in tropical regions but have been less so farther from the equator and closer to the poles. As global temperatures rise, however, the jet streams—westerly bands of fast winds that circle up to 9 miles above the Earth—are weakening and shifting in mid-latitude regions. That allows hurricanes and typhoons to form across a wider range.
Over the past 170 years, average global temperatures have risen two degrees Fahrenheit, according to a report issued in August by the Intergovernmental Panel on Climate Change. The report said temperatures would continue to rise by at least 0.7 degrees by 2100, attributing the phenomenon to greenhouse gas emissions “unequivocally caused by human activities," including the burning of fossil fuels.
The last time hurricanes formed at higher latitudes was during the Pliocene epoch, a period between 5.3 million and 2.6 million years ago marked by high temperatures and high levels of atmospheric carbon dioxide, according to the study.
“The tropical cyclones of the 21st century will most probably occupy a wider range of latitudes than at any time during the last three million years," Dr. Studholme said.
His group based the research on satellite observations of current weather as well as simulations of Earth’s past and projections of future weather. Such simulations have limitations, in part because they rely on incomplete data describing how the climate behaved in the past to project future patterns.
“It is very difficult to verify a climate model specifically for long-term multi-decadal changes in global tropical cyclones because of the uncertainty in observations," said Hiroyuki Murakami, a project scientist with NOAA’s Geophysical Fluid Dynamics Laboratory who wasn’t involved in the study. But, he added, it was “reasonable to infer the possible poleward shift in tropical cyclone latitudes in the future" based on the study.
In light of the potential threat, some cities aren’t waiting for precise information.
Last year, New York City Emergency Management updated the city’s coastal-storm plan, using new data to more accurately define areas most at risk of hurricane-related flooding and changing the boundaries of the city’s six hurricane evacuation zones accordingly.
The agency “continues to educate and prepare New Yorkers for the potential impacts of hurricanes, as climate change has increased their frequency and intensity," it said in a statement.
Boston is expanding efforts to prepare for a potentially wet and stormy future, in part by revamping waterfront parks with berms and flood walls to better manage rising waters, and building a new waterfront park designed to withstand hurricanes and catastrophic flooding, according to Rev. Mariama White-Hammond, the city’s chief of Environment, Energy and Open Spaces.
“With hurricanes, we don’t know how and when, but we already know where our low-lying areas are," she said. “We know enough to act."
