For many, reports of Hurricane Sandy's massive reach and destructive potential raised a simple question with a complex answer: Is this climate change?
The answer, experts say, is a qualified "yes."
Late-season hurricanes like Sandy aren't unusual. That the hurricane melded with a blast of Arctic air as it moved ashore, transforming into a powerful "post-tropical" nor'easter, is rare but not unprecedented. And scientists are quick to point out that they cannot yet definitively link an individual storm, like Sandy, to climate change.
But Kevin Trenberth, head of the climate analysis section at the National Center for Atmospheric Research, said it is likely that man-made global warming made Sandy stronger than it otherwise would have been.
Ocean temperatures along the East Coast were roughly 5 degrees Fahrenheit above normal as Sandy approached, and about 1 degree of that can be attributed to global warming, Trenberth said. Warmer ocean temperatures mean warmer air, which holds more moisture as it heats up, providing more energy for a storm like Sandy.
"With higher temperatures in the ocean and warmer air, the potential for the storm is simply to be greater, more intense, with especially heavier rainfall as a consequence," Trenberth said. "This, I think, is very clear. There is the role of global warming in this."
Jonathan Overpeck, co-director of the University of Arizona Institute of the Environment, agreed, as the debate over climate change's influence on Sandy heated up on Twitter on Monday night.
"Can't say [man-made climate change] caused it, but hard to imagine it didn't influence it & its impacts," Overpeck wrote. In addition to warmer seas and warmer, moister air adding fuel to storms like Sandy, he noted, sea level has also risen "significantly."
Sea-level rise increases damage
Several recent analyses have concluded that a huge swath of the East Coast is a sea-level rise hot spot. Seas from Cape Hatteras, N.C., to Boston are rising three to four times faster than the global average, according to one study published this summer in Nature Climate Change.
By the end of the century, that could add 7 to 12 inches of sea-level rise within the hot spot by 2100, on top of the 1 meter, or roughly 3.3 feet, that many scientists project will occur globally by 2100.
"Average sea-level rise over the 20th century was 1.8 millimeters per year," said Ken Miller, a geologist at Rutgers University. "Today, it's 3.2 millimeters per year. It certainly is accelerating. The question now is what's it going to do over the next 50 to 100 years."
Many scientists believe seas could rise another foot by 2050, Miller said, a change that is probably enough to turn a one-in-100-year storm to a one-in-20- or one-in-30-year storm in coastal New Jersey.
For low-lying beach communities, a matter of inches can mean the difference between overtopped dunes or levees and escaping a storm relatively unscathed.
"One of the most devastating aspects of this storm was surge," said J. Marshall Shepherd, a University of Georgia atmospheric scientist and president-elect of the American Meteorological Society. "As sea level continues to rise, whenever we get a storm like this -- or even a garden-variety storm -- we are going to see more damage."
The challenge now for communities in Sandy's path will be adapting to what New York Gov. Andrew Cuomo (D) called a "new reality."
"There has been a series of extreme weather incidents. That is not a political statement; that is a factual statement," Cuomo told reporters yesterday. "Anyone who says there's not a dramatic change in weather patterns, I think, is denying reality."
In New Jersey, Gov. Chris Christie (R) pledged to rebuild coastal communities, including the state's barrier islands, that were damaged as Sandy churned ashore, ripping out the boardwalk in the resort town of Seaside Heights and swamping low-lying Atlantic City.
"We'll rebuild it," he told reporters after a helicopter tour of the damage yesterday, the Asbury Park Press said. "No question in our mind, we'll rebuild it. But for those who are my age, it will be different."
A 'disconnect' between scientists and policymakers
For Shepherd, one of the "hidden stories" in Sandy's wake is the age of New York City's major infrastructure, including the sprawling subway system that links the five boroughs, which remains closed today as officials struggle to assess flood damage.
"Some of that infrastructure is not built for the storms of the future," Shepherd said. "For a lot of infrastructure in cities, they do engineering studies based on rainfall. But as our climate is changing, studies show it rains more and more intensely, we're seeing sea-level rise, and if we get stronger storms, our infrastructure is not built for them."
David Groves, a senior policy researcher at the RAND Corp., said that Sandy, like Hurricane Katrina before it, has exposed vulnerabilities that scientists were keenly aware of but may have surprised some coastal residents and government officials.
"The disconnect that exists is between scientists saying, 'This could happen,' and policymakers saying this is a high-enough priority to spend a lot of attention and resources on," Groves said. "It's always a challenge with things that don't happen very often and things that are devastating when they do."
Louisiana's devastating experience with Hurricanes Katrina and Rita in 2005 prompted the state to begin working on a new 50-year plan to stabilize its coastline, which is vulnerable to the combined effects of sea-level rise, storm surge and land that is slowly sinking.
One of the keys for the effort, which Groves has advised, has been finding a way to talk about climate change's impacts without turning off those who doubt climate change exists.
"Louisiana is not known for being on the forefront of climate change adaptation planning," he said. "Early drafts of the master plan were actually silent on the term 'climate change.' We addressed climate change factors, but it wasn't central to the story -- even though it was in the analysis. I think it was important that people realized that this is a problem, and an issue that could be exacerbated by climate change, but the problem is still there."
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