We've heard for years how climate change is making the weather more extreme. If you live between New York City and Boston, you're probably seeing the evidence outside your window tonight in the form of lots and lots (and lots) of snow. Both cities are at risk of breaking their all-time single-storm snowfall records (26.9 inches in 2006 and 27.5 inches in 2003, respectively).
That's quite a feat for the Northeast, which has some of the longest-running weather databases in the country (records have been kept continuously in NYC's Central Park since 1869). With up to 30 inches expected in New York City and "isolated totals of three feet" in the Boston area, this kind of snowstorm is very, very rare—"unprecedented," according to the National Weather Service.
When you look closer at the record books, a more ominous trend jumps out: Five of the ten biggest snowstorms in New York City have happened since 2003. This week's blizzard will likely make number six, bumping the 18-inch storm recorded on December 26, 1872, from the list. While climate change deniers will happily seize this as proof of a vast liberal conspiracy, the real question is more concerning: What if global warming is actually making snowstorms worse?
FiveThirtyEight's Nate Silver ran the numbers on Monday, posting a comprehensive analysis of extreme snowfalls for the last 100 years in New York City. He explains that although total snowfall in New York City has held steady over the last century, the number of snowy days has declined. He then tries to calculate the odds that such a trend would happen on its own—that is, without the help of increased evaporation from warmer oceans and possible changes in the jet stream.
The results show a very slim chance—between 0.2 and 4 percent, depending on how you calculate the numbers—that the city's recent snowstorm streak is just a fluke. Rather, the numbers suggest that the Earth's warming atmosphere is simultaneously eliminating smaller snowfalls and boosting big ones. Indeed, the Northeast is already seeing a boost in big storms, with a 71 percent increase in extreme precipitation since 1958.
But New York's big blizzard days may be numbered. The "sweet spot" for snow here is between 20 and 30 degrees Fahrenheit, and right now, the temperature still dips low enough for all the evaporated moisture caused by global warming to turn into snow. As the rate of climate change accelerates, the number of cold days will likely continue to dwindle, and so will the snowstorms.
We don't have to revert to advanced statistical analysis or atmospheric physics to know that climate change is making the impact of big storms worse. In a much more direct way the National Weather Service in Boston has been warning that this week's blizzard might permanently alter Massachusetts geography, with a storm surge that could create "one or more new inlets." The link to climate change is pretty obvious: Sea levels have risen about a foot or so across the Northeast over the last 100 years, about half of which is directly attributable to melting glaciers and warming oceans worldwide.
This may not come as a shock—most of us have been living with the realities of climate change for quite a while now. But the fact that we are seeing its effects in snowstorms should give us pause about what's to come.
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