If you live in the Northeast then you know that Hurricane Sandy is about to hit and if weather reports are to be believed, it’s going to be hit hard. New York City Subways systems have been shut down as of Sunday evening and cities have been taking precautions to minimized damage.
And while you may not immediately see a correlation between global warming and Hurricane Sandy, know that there is one. According to Dr Jeff Masters:
If Sandy makes landfall farther to the north near Maine and Nova Scotia, heavy rains will be the main threat, since the cold waters will weaken the storm significantly before landfall. The trees have fewer leaves farther to the north, which will reduce the amount of tree damage and power failures compared to a more southerly track. However, given that ocean temperatures along the Northeast U.S. coast are about 5°F above average, there will be an unusually large amount of water vapor available to make heavy rain. If the trough of low pressure approaching the East Coast taps into the large reservoir of cold air over Canada and pulls down a significant amount of Arctic air, the potential exists for the unusually moist air from Sandy to collide with this cold air from Canada and unleash the heaviest October rains ever recorded in the Northeast U.S., Nova Scotia, and New Brunswick. This Northeast U.S. scenario would probably cause damages near $100 million dollars.
And this isn’t the first time global warming-rainfall correlation has been stated. Earlier this year, we shared about a recent paper, published in Nature Geoscience, has found that global warming results in an increase in tropical rainfall. Specifically, according to author Paul O’Gorman, an atmospheric scientist at MIT, for every 1°C (1.8°F) increase in global average surface temperature, the rainfall in the tropics will increase by ten percent.
That’s a greater increase than scientists have already come up with for more temperate latitudes, a figure they’ve pegged at about five percent for every degree of warming. The disparity, O’Gorman said in an interview, is because the kind of rain patterns that affect the mid-latitudes and the tropics are different. Although you can get both widespread and localized rain events (such as thunderstorms) in both sorts of places, he said, local events are more common in the tropics.
“Because these are smaller in extent,” O’Gorman said, “climate models have more trouble representing them.” The result: projections for rainfall are all over the map, ranging from no increase at all to a leap of 25 percent for every degree of warming, depending on which model you choose.
So O’Gorman came at the problem in a different way. He looked at how climate models deal with rainfall changes caused, not by global warming, but by the naturally occurring El Niño—Southern Oscillation (ENSO) phenomenon, in which the eastern equatorial Pacific Ocean warms up for a year or two, then cools back down. “ENSO isn’t generally a good proxy for global warming,” O’Gorman said, “because it’s a regional event. It causes an increase in rainfall in some areas and a decrease in others.”