Warming climate makes extreme rain events worse, experts say - WMUR Manchester

Warming NH climate makes extreme rain events worse, experts say

Warming climate makes extreme rain events worse, experts say

New Hampshire's summer marked by heavy downpours, flooding

This summer has been marked by intense rain in New Hampshire, and scientists said that could be a symptom of a warming climate.

A remarkably active weather pattern over the Northeast dropped anywhere between 6 and 12 inches of rainfall across New Hampshire in July, causing flash flooding and washing out roads.

While all the rain can't be directly attributed to climate change, it's clear that such extremes are happening more and worsening.

"What climate change does to weather patterns is to kind of ramp them up a bit and increase the extremes," said state climatologist Mary Stampone.

New Hampshire is no stranger to summertime downpours and thunderstorms, but Stampone said it's unusual to see such extreme amounts of rainfall in such a short amount of time.

"This time of year, we get more of our storms to come in from the west with frontal systems that tend to produce these heavier rain events," Stampone said. "Then, you add in climate change, which increases the amount of precipitation that falls within these events, and you just have the right mixture for repeated flood events."

Western and central New Hampshire were hit especially hard by July's tropical rainfall. Roads buckled underneath rushing rapids, and in Swanzey, a campground had to be evacuated during rising floodwaters as other roads were destroyed.

In mid-July, a person had to be rescued from a car that got stuck in floodwaters in downtown Manchester. The same storm system devastated roads in Alton.

Just to the north, in Madison, a section of Route 113 collapsed, leaving residents stranded and cars buried in debris.

"We've seen an increase of about 40% in extreme precipitation," said Jonathan Winter, a climate scientist at Dartmouth College. "By the end of the century, we'll get about 50% more extreme precipitation."

Winter said rising temperatures will allow the atmosphere to hold more water vapor. That could lead to heavy rain events becoming even more intense.

"And you can think of the atmosphere now as being a bigger bucket," he said. "Whereas before, you had this medium-size bucket, and when you got the right conditions, that medium-size bucket got dumped on you as your downpour, and that was your extreme precipitation event. Now, climate change has made this bucket bigger."