Extreme precipitation in the Northeast linked to human activity

An abrupt increase in extreme precipitation across the northeastern United States is part of a larger trend, according to a new study from Dartmouth College. 

States from West Virginia to Maine have experienced heavier rain and snowfall since 1996. The experts found that this excess precipitation has coincided with warming sea surface temperatures in the North Atlantic. 

Extreme precipitation in the Northeast is typically caused by tropical cyclones, thunderstorms, and extratropical cyclones like Nor’easters.

The new study has linked the last 25 years of extreme precipitation in the Northeast to greenhouse gases from human activity and a warming Atlantic Ocean.

“Our previous work has shown that Northeast extreme precipitation has increased dramatically over the past 25 years, but this study is among the first to demonstrate that this rise is partially due to anthropogenic climate change,” said study lead author Huanping Huang.

In an earlier study, the Dartmouth team found that the Northeast has experienced a 53 percent increase in extreme precipitation since 1996, and that the primary driver of the increase is heavier rainfall from tropical cyclones. 

The researchers linked this weather phenomenon to a warmer atmosphere – which can hold more water – and to a warmer Atlantic Ocean – which drives stronger and more frequent hurricanes. 

“Our results demonstrate that multidecadal variability in Atlantic sea surface temperatures, an important driver of warming in the Atlantic, alongside anthropogenic greenhouse gases and aerosols, also contributed to the increase in Northeast extreme precipitation after 1996,” explained Huang.

The warming of the North Atlantic Ocean since the 1990s is tied to both natural variability and an increase in greenhouse gases. This warming is also tied to a decrease in aerosols, which pollute the air and reflect sunlight, creating a cooling effect. 

“Our analysis illustrates that decreased aerosols and increased greenhouse gases from human activity have contributed to both the rise in Northeast extreme precipitation and North Atlantic sea surface temperatures,” said study co-author Professor Jonathan Winter. 

“Our research team has been exploring this dramatic increase in extreme precipitation for several years now, and this study confirms that humans are in fact, partially responsible for the increase in heavy rain events that we have been experiencing over the past two and a half decades.”

The study is published in the journal Weather and Climate Extremes.

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By Chrissy Sexton, Earth.com Staff Writer