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New research from Dartmouth shows increase in extreme precipitation in the Northeast by the end of the century

Road damage after heavy rainfall in Conway, NH
Mara Hoplamazian / NHPR file photo
Road damage after heavy rainfall in Conway, NH

Climate change is driving an increase in extreme precipitation across the Northeast, according to a new study from Dartmouth.

The research shows events that bring 1.5 inches or more of heavy rainfall or melted snowfall in one day are expected to increase 52% by the end of the century.

Jonathan Winter, a Dartmouth professor and a senior author on the study, said climate change can influence rain in a variety of ways. But the key idea, he said, is that a warmer atmosphere can hold more water vapor.

“When you have a warmer atmosphere under a warmer climate, when you get the conditions that are right for precipitation, because you have more of it in the atmosphere, it becomes these heavier rainfall events and is then classified as extreme precipitation,” he said.

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Winter says the increase in extreme precipitation is expected to happen mostly in the wintertime and the spring, with wintertime precipitation expected to more than double. As the climate warms, more snow is expected to fall instead as rain.

Researchers are expecting a large increase in the number of days with extreme rain or snow, and a smaller increase in the amount of precipitation during each event.

The study comes after Winter and his colleagues’ previous research showed that there has already been about a 50% increase in extreme precipitation from 1996 to 2014, also linked to climate change.

To examine future precipitation, the researchers used a climate model to simulate rain and snowfall between 1976 and 2005, and to simulate what’s expected between 2070 and 2099. They compared the results to a set of 16 other models, which showed largely consistent results.

“If anything, we're a little bit on the conservative end,” Winter said.

Some communities in New Hampshire are already experiencing more frequent flooding, and trying to plan for the effects of climate change on roads and other public resources. Winter says projections for precipitation in a warmer climate can help with planning for things like natural disasters, stormwater management, and zoning.

“What this hopefully gives some insight into is: we should be careful about relying too much on the past because it's not a good proxy for what's going to happen in the future,” he said.

Mara Hoplamazian reports on climate change, energy, and the environment for NHPR.
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