This time, the preparations are a little more familiar. We would have had a few gallons of bottled water left over from Irene, but we'd moved and left them behind. Last time, we bought canned stew that, when finally consumed for lunch months later, turned out to be almost too salty to eat. This time, we bought low-sodium chili and canned ravioli stamped with the USDA organic seal of approval, optimistic that it will means the can's contents are more palatable than Chef Boyardee. We may or may not have procured too many bagels.
Is this what climate change feels like? New York City is grinding to a stand-still (although Wall Street will keep working as long as the power is on and the web connections are solid). The city feels drearier, a little more routine than it did during Irene, when the party-hardy resolved to drink right through the hurricane. That storm turned out to be a bust in the city, while upstate flooding ruined crops, took out roads, and caused billions of dollars in damage. The winds and storm surges coming with Hurricane Sandy seem more likely to hit New York City directly.
It takes a good long while and a fair bit of effort for scientists to feel comfortable saying that any particular storm, drought, or heat wave was caused by man-made climate change. To talk about these connections requires a vocabulary of likelihoods and probabilities. The International Panel on Climate Change will say, for instance, that it is "very likely" that, worldwide, the number of warm days and nights has increased and "likely" that same trend holds true in North America and Europe. As nine out of the ten hottest years on records occurred during the 21st century, it might seem, to a layman, that it is more than "very likely"-really, just common sense-that there have been more hot days and nights lately. But because so many factors influence the weather, climate scientists are careful about the weight they give to climate change's impacts. Linking climate to events like droughts or hurricanes poses a particular challenge: As the IPCC wrote in a recent report, "Extreme events are rare, which means there are few data available to make assessments regarding changes in their frequency or intensity. The more rare the event the more difficult it is to identify long-term changes."
But it is possible. Last fall, two researchers from the Potsdam Institute for Climate Impact Research published a study that linked the Russian heat wave of 2010 to rising global temperatures by running, tens of thousands of times, a simulation that modeled summer temperatures. They modeled both a world in which climate change was happening and in the world in which it was not. They found that the heat wave might have happened in a world without climate change, but it was much more likely to have happened in a world where climate change exists-so much more likely that they could conclude that there is "an approximate 80 percent probability that the 2010 July heat record would not have occurred without climate warming."
Then, this summer, climate scientist James Hansen, who, for as long as anyone has been talking about climate change, has been accurate but aggressive in communicating its risks, went further. He wrote in The Washington Post that it was time to drop the caveat that "no individual weather event can be directly linked to climate change." Hansen and his colleagues had just completed a study that showed how much more frequent extremely hot temperatures were becoming around to globe. For the Russian heat wave in 2010, along with another in Europe in 2003, and the drought last year in Texas, "there is virtually no explanation other than climate change," Hansen wrote.
While studies have linked heat waves across the globe to climate change, scientists are less certain how rising temperatures will affect the formation of hurricanes: They're not sure that climate change will lead to more hurricanes, although it's safe to say that warmer waters, warmer air, and higher seas could make the hurricanes that do come hurt more.
However likely it is that this particular, strange storm has come because of climate change, this new routine-waiting, watching, wondering how bad it will be this time, whether the storm will hit here or there, if the heat will let up today, tomorrow, or after the crops have shriveled-it will become more familiar as the world warms up. What is certain about climate change is that it will bring more disastrous weather along with it. Heat waves won't be more predictable, but they'll be more frequent. Storm surges will threaten more homes. Scientists may hesitate to link weather and climate, but laymen do not. This year, Americans started believing in climate change again: the Yale Project on Climate Change Communication found that for the first time in four years, more than 50 percent thought climate change was real and caused by human activities. And three-quarters of Americans that the project surveyed at the beginning of September believed global warming had something to do with the terribly hot summer they'd just lived through.
Here is what it's possible to say for certain: Climate change is happening. It's likely that we'll get better at dealing with erratic and extreme weather. There's a high probability that, over the next decades, we'll worry more often about crops dying and about monster storms. And just as it's almost normal now for each passing year to be one of the hottest ten on record, soon it may seem routine to hear that the hurricane that's currently headed towards your city is the largest ever measured. The two men running for president did not mention this issue when they met in three debates, and neither has shown much interest in addressing it in the next four years. But if the summers stay hot and the hurricanes abnormally large, enough people might start believing that climate change is problem that they'll have to.
