New Hampshire experienced more days over 90 degrees and higher average and overnight temperatures in the summers over the past 50 years, as human activity has warmed the planet.
Warming temperatures represent a stress on people and the essential infrastructure on which they rely, according to UNH professor Jennifer Jacobs, the lead author of the transportation section of the last National Climate Assessment, in 2018.
“We’ve been watching these summer heat waves that keep increasing since the 1960s – these extremes that have short-term and long-term impacts on transportation,” she said.
The sustained heat New Hampshire is seeing right now could cause some highway areas to soften, allowing vehicles to leave ruts in the pavement as they go by, she said.
“The materials are pretty warm all the way through at this point, so they’re more vulnerable to that kind of damage,” she said.
Jacobs said spikes in temperature also make tire shredding and blowouts more likely for trucks. And she said the heat can be a distraction or health threat for work crews and drivers at the peak of construction season, posing extra safety risks.
During the heat, the National Weather Service recommends everyone drink plenty of fluids, stay in air conditioned locations if possible and to check up on family, friends and neighbors who may be alone and need help.
A 2019 study from the Union of Concerned Scientists found that even with some action to curb global carbon emissions, New Hampshire would see 2 to 3 weeks’ worth of days that feel hotter than 90 within the next several decades. The “feels-like” measure of heat accounts for humidity as well as temperature.
If emissions remain on their current trajectory, the study found, the state could see about 6 days a year that feel hotter than 100 degrees by mid-century, and 19 days by late century. Historically, there have been none.
And this change is already happening: Analysis by the nonprofit Climate Central shows that since 1970, Concord has seen five more days a year on average over 90 degrees Fahrenheit. Manchester has seen two more.
The average overnight low in the summer has increased about 3 degrees in Concord and Manchester. And the average summer temperature is 2.3 degrees higher in Concord, and 1.5 degrees higher in Manchester, than it was 50 years ago.
It poses a paradoxical challenge to another aspect of infrastructure in places like New England, where air conditioning and heat-protected electrical and mechanical equipment are less common than in other, historically hotter parts of the country.
More heat will mean more demand for cooling – but cooling requires electricity, which creates more planet-warming carbon emissions when powered by fossil fuels.
Currently, New England gets about half of its power from natural gas. On days when the grid sees very high demand due to weather, reserves of coal and oil can be called into use at plants like Merrimack Station in Bow.
“Our infrastructure depends on the power grid – whether it’s traffic lights, whether it’s emergency signals,” Jacobs said. “[When] the power grid starts getting stressed in these types of temperatures just because of the demands on it, then we start getting a little bit concerned about that.”
The risk of rolling blackouts is lower here than in other parts of the country – New England runs with a much higher margin of power in reserve than, for example, Texas. But energy costs are higher here, and energy use during heat waves can drive them up.
In the coming years, the region and President Joe Biden’s administration hope to build out huge amounts of zero-carbon offshore wind energy, as well as renewable-powered energy storage, to help limit prices and strain on the grid on extreme weather days.