There’s no clear answer to the raging scientific debate over whether climate change, including record low levels of sea ice in the Arctic this summer, influenced Hurricane Sandy’s path and intensity.
But scientists agree on one point: Rising sea levels caused primarily by global warming could worsen the effects of storms such as Sandy, particularly when it comes to storm surge. And that means coastal communities throughout the United States must think about what they’ll need for protection from such storms.
"The economic impacts go from Florida to Maine," said Leonard Berry, the director of the Climate Change Initiative at Florida Atlantic University in Boca Raton. "Whatever you think about global warming, it suggests we’re dealing with a different scenario of storms and patterns of rainfall, which is going to be exacerbated by even the small rise in sea level which we’ve already had."
In hard-hit New York, that means rebuilding flooded subway tunnels in the short term and in the long term, perhaps constructing a multi-billion-dollar flood barrier to protect lower Manhattan from the sort of storm surge it experienced during Sandy. In places such as Punta Gorda, Fla., which was swamped by waters from the Gulf of Mexico during Hurricane Charley in 2004, it means rethinking coastal land uses and possibly abandoning some to the sea.
“It’s a longer conversation, but I think part of learning from this is the recognition that climate change is a reality; extreme weather is a reality; it is a reality that we are vulnerable," New York Gov. Andrew Cuomo, a Democrat, said Wednesday in a news briefing about storm recovery. "The frequency is way up. It is not prudent to sit here, I believe, to sit here and say it’s not going to happen again. Protecting this state from coastal flooding is a massive, massive undertaking. But it’s a conversation I think is overdue."
Climate change got short shrift this election season. It didn’t come up during the presidential or vice-presidential debates, a first since 1984. President Barack Obama did mention it during the Democratic National Convention, telling delegates that "climate change is not a hoax" and vowing to approach energy policy in a way that he said would "continue to reduce the carbon pollution that is heating our planet."
During the Republican convention and on the campaign trail, opponent Mitt Romney has bashed Obama repeatedly for his 2008 promise to "begin to slow the rise of the oceans and heal the planet."
Environmental groups have been agitating for more discussions of climate change, and they’ve used Sandy as an illustration of what many consider a global problem. The Climate Reality Project, founded by former Vice President Al Gore, called Wednesday for the political debate to "catch up with the reality of the climate crisis.”
"The facts are clear: Climate change is happening now, and devastating extreme weather has become more frequent and more severe," CEO Maggie Fox said. "Sea levels have been rising at alarming rates, making storm surges that come with all storms more damaging. With super storms like Sandy, the surges are devastating."
New York Mayor Michael Bloomberg said that even if the direct cause of Sandy’s severity was unknown, cities must recognize that something has changed.
"What is clear is that the storms that we’ve experienced in the last year or so around this country and around the world are much more severe than before," Bloomberg said Tuesday. "Whether that’s global warming or what, I don’t know. But we’ll have to address those issues."
Sandy resulted from the chance alignment of several weather systems, including a winter storm that dumped snow on Colorado, said Kevin Trenberth, a senior scientist at the National Center for Atmospheric Research, a federally funded research and development center.
But a human influence was present, too, he said. From the Carolinas to Canada, sea surface temperatures just before the storm were about 5 degrees Fahrenheit above the 30-year average for this time of year. About 1 degree is "very likely a direct result of global warming," Trenberth wrote in an article explaining the role of climate change in the storm.
With every degree Farenheit rise in temperature, the atmosphere can hold 4 percent more moisture. As a result, Trenberth said, Sandy was able to pull in more moisture, fueling a stronger storm and magnifying the amount of rainfall by as much as 5 to 10 percent compared with conditions more than 40 years ago.
Coupled with higher sea levels – since 1992, satellites have observed a 2.25-inch rise – that means more water to surge onshore and penetrate farther.
"That may not sound like a lot," Trenberth said in an interview. But "a small increase in sea level can actually make a big difference."
Ben Strauss, the director of the sea level-rise program at the Princeton, N.J.-based research group Climate Central, warned Congress in testimony last spring that over the long term, the rising sea level will force cartographers to redraw the map of the United States. It’s enough to turn Miami-Dade County in Florida "into a collection of islands," he said in his testimony.
Short term, it means more coastal flooding during severe storms, as was seen in New York City and along the New Jersey shore.
"Storm surge is basically the most damaging part of most hurricanes, not the wind," Strauss said in an interview from New York. "Sea level rise has been increasing the damage from coastal flooding in every hurricane. The more sea level rises, the more that will be the case."