September 3, 2013
Hurricanes Become Less Threatening To US Coast, Based On Climate Models
[ Watch the Video: Climate Change Could Push Hurricanes Away From The East Coast ]
Lawrence LeBlond for redOrbit.com - Your Universe OnlineRecent studies have painted a pretty grim picture for future hurricane seasons, with more frequent and intense storms occurring in the Northeast due to a changing climate. Last year’s superstorm Hurricane Sandy was labeled as evidence of such climatic storms impacting the US Atlantic coast.
However, a new study by researchers from Columbia University and Colorado State University is suggesting climate change could eventually keep such hurricanes from making a sizeable impact on US coastlines. Publishing the findings in the journal Proceedings of the National Academy of Sciences (PNAS), the researchers said climate shifts could push future hurricanes away from the East Coast.
More appropriately, the team of researchers says manmade greenhouse gases could actually redirect atmospheric winds that steer these hurricanes. While experts are generally in concurrence that climate change will produce stronger hurricanes in the future and may even produce more frequent storms, there is building evidence that most of the East Coast will be at much lower risk of taking a direct hit in the future.
So, for those who are rebuilding their lives in the wake of the devastating superstorm Sandy, there should be some solace in knowing that another storm of equal size and destruction is not likely to strike the region again anytime soon. In fact, the odds of a storm similar to Sandy impacting the East Coast again is extremely remote – a once in 700 year event, according to the researchers.
However, they say it may be premature to celebrate just yet. The team said there are other factors that also must be accounted for in predicting storm frequency and direction. As global warming continues its wrath, sea levels will continue to rise and stronger storms will still likely be produced, which could possibly outweigh changes in the steering currents predicted by the study’s computer models.
"Sandy was an extremely unusual storm in several respects and pretty freaky. And some of those things that make it more freaky may happen less in the future," study coauthor Adam Sobel, an atmospheric scientist with Columbia University, told the Associated Press. However, he added, "There's nothing to get complacent about coming out of this research."
This study looks mainly at jet stream forecasts. Several recent studies have highlighted unusual jet stream forecasts, linking the currents to extreme weather events and loss of sea ice in the Arctic. The new study, however, sees less swerving in the future of the jet stream, which would make the case for less turning of hurricanes, keeping them out of the US.
"What made Sandy so different was that it was steered into the coast rather than away from it," Elizabeth Barnes, a climate scientist at Colorado State University and an author of the study, tol Suzanne Goldenberg of The Guardian.
The researchers used climate models to study whether future atmospheric conditions would be more or less likely to blow a storm similar to Sandy westward into the Atlantic coast. The team used a scenario of triple the amount of greenhouse gas emissions by 2100 in their models.
They discovered that future air patterns under climate change actually make a repeat event less likely. The models actually show changes in the jet stream more likely pushing such storms further offshore, away from populous coastal regions along the Atlantic seaboard.
As for Hurricane Sandy, researchers are in agreement that the unusual track was caused by a rare interaction between the jet stream and a high-pressure weather system known as a “blocking system” to the north of the hurricane. This interaction caused Sandy to hook left and make landfall in New Jersey, when normally it should have continued on a more northeasterly track.
The authors of the new study said that Sandy’s track was the most perpendicular to the East Coast of any storm on record.
With the new climate change predictions, the trajectory that was observed in Sandy would be less likely to recur. A change in the atmospheric winds would reduce the odds of a high-pressure blocking system similar to the one that affected Sandy’s path from forming, helping to keep such massive storms from impacting American shorelines.
EXTENDED HURRICANE SEASON
The study’s findings have not been accepted by all experts, however.
Some meteorologists, such as Jennifer Francis of Rutgers University, said this study may contribute to an understanding of how climate changes affect the future of weather patterns, but she is not convinced their computer models are as accurate as they portray.
"In my view, the analysis and results from this and other recent studies do not support the strong statements made by the authors," she told National Geographic’s Willie Drye.
Jeff Masters, a meteorologist with Weather Underground, said there are indications that hurricane seasons have lasted longer in recent decades and may continue to do so. Typically, hurricane seasons last from June 1 to November 30; warming seas could extend the seasons, he noted.
"A longer season gives the opportunity for more strong hurricanes to penetrate to the Northeast U.S. in late fall," Masters told NatGeo. "This would potentially offset any decrease in Sandy-like impacts due to fewer blocking highs forming in a future climate."
Barnes acknowledged that the computer models are not 100 percent accurate and that hurricane seasons could be longer due to warming seas and other factors.
"We comment on that in this paper," she said. "The point one should take from our paper is just that these are the best climate models we have, and they do not support the notion that the kind of steering flow that occurred in Sandy will become more frequent in a warming climate."
Kerry Emanuel, a professor of meteorology at MIT who edited the authors’ paper, said that “changing steering patterns are only a part of the whole problem of how and whether hurricane risk may change in a particular place."
"One must also account for changing locations and times of storm formation, and changing storm frequency and intensity," Emanuel told NatGeo. "These can very much change the landscape of hurricane risk, so one should be careful in drawing overall conclusions about such risk from just one piece of this problem."
Emanuel authored a paper last year that found there would be an increase in major hurricanes under climate change, with up to 20 additional hurricanes and tropical storms every year by the end of the century. However, that study doesn’t give estimates on where such storms would likely hit.
"What they did in this paper was to look specifically at the steering patterns in the atmosphere," Emanuel told The Guardian. Hurricanes and tropical storms that stay out at sea pose less of a threat. But he added: "It doesn't mean that New York is off the hook if in fact there are going to be more storms overall."
"There is no question that there is potential for larger destruction from storms and more damage from storms even though the track is going further offshore," Emanuel said.
Barnes concluded that the connections between hurricanes and climate change were still not clearly understood and more research is likely needed. “this is just one part of the puzzle,” she said.