Experts say Sandy is a sign of more to come. “As the world warms and these storms become more frequent, we're going to be caught out again,” says Michael Oppenheimer, a geosciences professor at Princeton University who has been studying climate change for three decades.
Because climate is enormously complex, no particular storm can be attributed to climate change. We can, however, say that the storm fits a general pattern in North America, and around the world, toward more extreme weather—a pattern which, increasingly, can be attributed to climate change.
Warmer oceans provide more energy for storms.
The ocean is warming along with Earth’s atmosphere. Tropical cyclones—also called hurricanes or typhoons—are the most powerful storms on Earth and feed on warm waters at the ocean surface. Warmer waters provide more energy for these storms, making them more powerful. Intense and destructive storms are likely to become more and more frequent as our planet continues to warm. In fact, they already have. Also, warmer air retains more moisture, which is drawn into storms and dumped on us in the form of heavy rain or snow.
Climate change is causing sea level to rise.
Sea level is rising because the ocean is warming, and warmer water expands. Warmer temperatures also melt ice sheets and glaciers, which increases the amount of water in the ocean. Sea level has risen on average by about 7 inches (15 centimeters) since 1900, and even higher along the East Coast.
Higher sea levels increase the impact of storms.
As we can see from devastation in coastal New Jersey, Staten Island, and low-lying Brooklyn neighborhoods, storm surges are the most damaging aspect of tropical cyclones. “One link between hurricanes and climate change is very precise. That’s the vulnerability of coastal cities to hurricane impacts, and that’s linked to sea-level rise,” says Ben Orlove, co-director of Columbia University’s Center for Research on Environmental Decisions. “This was essentially what we thought of as the once-in-a-100-years event,” says Radley Horton, of Columbia’s Center for Climate Systems Research and a NASA scientist specializing in climate projections. “As sea levels rise, we'll see these types of events more often.”
An article in Nature Climate Change, by Kerry Emanuel, Michael Oppenheimer, and Erik Vanmarcke puts it this way: “The combined effects of storm climatology change and a one meter sea-level rise may cause the present NYC 100-yr surge flooding to occur every 3-20 years and the present 500-yr flooding to occur every 25-240 years by the end of the century.” As sea levels continue to rise, it won’t take hurricanes as big as Sandy to wreak havoc along the East Coast.
We understand the forces that create big storms much better than we used to.
While it’s impossible to tease out precise effects that each climate variable, such as sea-level rise, storm surge, and high tide, had on Sandy’s size and strength, there’s no doubt that this century’s sea-level rise made the megastorm worse. And over the past decade, climate scientists have gotten very good at determining what affects the variables that create big storms—and their link to climate change.
So how did climate change contribute to Sandy’s size and strength?
Sandy was also fueled by much-higher-than-average sea-surface temperatures along the East Coast, where ocean water is still warm this time of year, pumping energy into the swirling system—with about 15 percent of the temperature increase attributed to climate change, according to Katharine Hayhoe, an associate professor of atmospheric sciences at Texas Tech University. And record loss of sea ice in the Arctic this year may have steered Sandy towards the coast. Emerging research suggests that as more Arctic sea ice melts in the summer—because of global warming—atmospheric circulation patterns will change, including the path of the jet stream. That may make it easier for storms to stagnate in the North Atlantic or even move west, as Sandy did.
“Of course we don’t know what the future will bring, but we would be well served as a society by understanding that climate change is increasing the risk of major disasters,” says Curator Ed Mathez, a geologist in the Museum’s Department of Earth and Planetary Sciences. “These include not just cyclones, but also floods, extensive droughts, and widespread famines. We have to start asking ourselves what such events could cost society.”