UNH Today

A pair of devastating hurricanes battered the southeastern U.S. over the last three weeks, leaving in their wake enormous swaths of flooding and destruction. While hurricanes are hardly atypical at this time of year, storms like Helene and Milton are becoming increasingly more intense, thanks in large part to the changing climate and warming seas.

Given that trend, is there a world where storms of that magnitude make their way to New England in the not-too-distant future?

The short answer is no – Category 5 hurricanes as Milton was initially designated are unlikely to become an issue in the region, fended off by colder temperatures, says Mary Stampone, associate professor of geography at UNH and New Hampshire state climatologist.

But the longer answer is a bit more nuanced. While New England is unlikely to see the treacherous winds connected to major hurricanes like Helene and Milton – category designations for hurricanes are based solely on measured wind speeds – significant rainfall and inland flooding remain a growing threat as storms intensify and sustain strength due to climate change, including regional menace nor’easters.

“A storm can maintain its tropical characteristics further north now than it used to be able to because of the warming sea surface. And a Category 1 storm can still drop a ton of rain,” Stampone says, pointing to Hurricane Irene, which made landfall as a Category 1 storm in 2011 and downgraded to a tropical storm as it crossed northern New England. “These storms themselves are not caused by climate change – they would have formed anyway – but the intensity and size of the storms can be attributed to it.”

The primary culprit for that surge in storm power is the warming sea surface – and New England happens to be positioned alongside the fastest-warming area of ocean in the world, the Gulf of Maine. And while that isn’t likely to suddenly produce major hurricanes in the area, it is adding dangerous fuel to storms more native to the region.

“The same thing that’s happening to hurricanes is happening to nor’easters – warmer ocean temps are pumping more heat and water into the storms, so they are getting bigger, wind speeds are getting stronger and they’re producing more precipitation,” Stampone says. “As winters warm, nor’easters can pack everything under the sun – you can get blizzard conditions, you can get ice storms, you can get heavy flooding rain, and a little farther south you can get thunderstorms that produce tornadoes. The stronger they get, the more of that they are going to bring.”

Other conditions have already raised the threat alert, according to Stampone’s research. She is a co-author of the New Hampshire Coastal Flood Risk Summary Part 1: Science that found sea-level along the coast in New Hampshire and southern Maine has risen almost 8 inches in the last century, impacting coastal property, public infrastructure, human health, public safety, economy and natural resources, especially during nor’easters and high astronomical tides.

She was also co-author of the 2021 N.H. Climate Assessment Report which points to a warmer and longer spring and fall and shows that annual rainfall is expected to increase another 7% to 9% by the middle of the century.

Nationally, Helene and Milton are the latest examples of the impact climate change is having on increased strength and reach of storms and the devastation they can produce (An AP story estimates they could each be $50 billion disasters, putting them in the company of hurricanes Katrina, Sandy and Harvey). Whereas non-coastal locales like the mountains of western North Carolina wouldn’t have had to worry about hurricane impact 20 or so years ago, the ability of the storms to pack more rain make destruction like that seen from Helene a growing reality. Inland flooding is becoming “an incredible hazard,” Stampone says.

Strengthening storms cause significant challenges in preparedness, too, Stampone notes. Storms are spinning up and progressing through categories much faster – Milton went from a tropical storm to a Category 5 hurricane in less than a day – making it exceedingly difficult to warn residents or leave multiple days to coordinate evacuation plans.

The best hope of slowing that continued progression is societal intervention via a combination of adaptation and mitigation, Stampone says. Things like restoring coastal wetlands – which store large amounts of carbon but also soak up water when there is a storm surge – and investing in renewable energy infrastructure are approaches that could make a significant difference.

That message is particularly vital in the wake of Hurricanes Helene and Milton. Since storms like that duo are becoming increasingly more intense, now is the time for urgency in response, says Stampone. And though communities understandably often feel helpless in the moments when significant storms hit, she remains hopeful that change can be enacted.

“Climate change isn’t a future thing – it’s here, we are in it. This is not decades down the road anymore, we are being impacted by it. But we still have time to avoid the worst of it if we invest in mitigation efforts now,” Stampone says. “All is not lost. We can still do something.”