It’s one of the classic predictions of global-warming science: as the planet heats up, extreme precipitation should become more common. That’s because warm air can hold more moisture than cool air, and when that moisture finally comes down as rain or snow, there’s more of it to fall.
Exactly how much more, however, is something scientists are still working out — and a paper just published in Nature Geoscience has taken a step in that direction. According to author Paul O’Gorman, an atmospheric scientist at MIT, heavy downpours in the tropics are likely to increase by ten percent for every 1°C (1.8°F) increase in global average surface temperature. 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.