Drought intensity and frequency has been decreasing in the Northeast since the mid-1980s, according to a new study from Dartmouth, despite predictions. Published in the Journal of Hydrometeorology, the report says that heavier precipitation has counteracted potential drying caused by rising temperatures.
The report looked at historical weather data from 1901-2022. Since the early 1980s, earth’s temperature has risen at an increasingly rapid rate, according to the National Oceanic and Atmospheric Administration.
These rising temperatures have changed how water moves through the environment. Jonathan Winter, the report's lead author and a professor of geography at Dartmouth, said that warming temperatures ramp up evaporation and transpiration, meaning more water leaves soils, lakes and plants and goes into the atmosphere, because a warmer atmosphere can hold more moisture.
“So all other things being equal, we would see an increase in drought in the Northeast,” he said. But, the study showed, all things have not been equal. The report found that the period from 1984 - 2022 was wetter than the period from 1901-1983 and had fewer and less intense droughts
Because a warmer atmosphere retains more moisture, it leads to more intense rainfall.
“We know that climate change is making extreme precipitation worse and that extreme precipitation has gotten worse,” Winter said.
But Winter underscored the limited scope of the study, noting that it only summarizes historical trends and does not make projections about drought in the future.
“A difficulty with this finding is to lull people into a false sense of security that climate change will never make drought worse, or that New England will never have droughts in the future,” he said. “At some point in the future, it might be the case that those warmer temperatures end up pushing us more towards drought because the precipitation simply can't catch up.”
Climate change is changing global and local weather patterns. New Hampshire is becoming warmer and wetter, but scientists also predict an increased risk of short-term drought in between increasingly extreme rain and snow events.
The western U.S. has experienced increasingly severe drought conditions in recent years, Winter said, because its water scale has been tipped in the opposite direction than the Northeast’s.
“They have not had additional snowpack or additional rain that's refilling their reservoirs to the extent that they're covering any losses due to warmer temperatures,” he said.
The study also found weather has not become more volatile in the Northeast, with no changes in swings from wet and dry events over the last century.
