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Passengers exit a subway train at the Times Square station in New York on Thursday. (AP)
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Nov. 1: From the darkened living rooms of Lower Manhattan to the wave-battered shores of Lake Michigan, the question is occurring to millions of people at once: Did the enormous scale and damage from Hurricane Sandy have anything to do with climate change?
Hesitantly, climate scientists offered an answer this week that is likely to satisfy no one, themselves included. They simply do not know for sure if the storm was caused or made worse by human-induced global warming.
They do know, however, that the resulting storm surge along the Atlantic coast was almost certainly intensified by decades of sea-level rise linked to human emissions of greenhouse gases. And they emphasised that Hurricane Sandy, whatever its causes, should be seen as a foretaste of trouble to come as the seas rise faster, the risks of climate change accumulate and the political system fails to respond.
“We’re changing the environment — it’s very clear,” said Thomas R. Knutson, a research meteorologist with the government’s Geophysical Fluid Dynamics Laboratory in Princeton, New Jersey. “We’re changing global temperature, we’re changing atmospheric moisture, we’re changing a lot of things. Humans are running this experiment, and we’re not quite sure how it’s going to turn out.”
By the time Hurricane Sandy hit the Northeast coast on Monday, upending lives across the eastern half of the country, it had become a freakish hybrid of a large, late-season hurricane and a winter storm more typical of the middle latitudes. Though by no means unprecedented, that type of hybrid storm is rare enough that scientists have not studied whether it is likely to become more common in a warming climate.
“My profession hasn’t done its homework,” said Kerry A. Emanuel, a climate scientist at the Massachusetts Institute of Technology. “I think there’s going to be a ton of papers that come out of this, but it’s going to take a couple of years.” Scientists note that a warmer atmosphere can hold more water vapour, which in principle supplies more energy for storms of all types.
The statistics seem to show that certain types of weather extremes, notably heat waves and heavy downpours, are becoming more common.
But how those general principles will influence hurricanes has long been a murky and contentious area of climate science. Most scientists expect that the number of Atlantic hurricanes will actually stay steady or decline in coming decades as the climate warms, but that the proportion of intense, damaging storms is likely to rise.
The experts differ sharply on whether such a rise can already be detected in hurricane statistics. Recent decades seem to show an increase in hurricane strength, but hurricanes tend to rise and fall in a recurring cycle over time, so it is possible that natural variability accounts for the recent trends.
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