In celluloid imaginings, hot summer nights are sultry… steamy… dangerous.
They are all that. Add increasingly common, unhealthy and not so great for the environment.
What meteorologists and weather-watchers are finding during hot spells like we’ve had this month is not just that daytime highs are high. It’s that nighttime lows aren’t as low as they used to be. In a warming world, we don’t cool off as much when the sun goes down.
“On average, temperatures at night are warmer,” said Gary Lessor, director of The Weather Center at Western Connecticut State University in Danbury. “We’re about 5 degrees above normal for the month of July.”
“The highs and the lows at night are both high,” said Bill Jacquemin, senior meteorologist at The Connecticut Weather Center in Danbury.
The Cary Institute for Ecosystems Studies in Millbrook, N.Y., has had its own weather station for 31 years. Vicky Kelly, manager of the institute’s environmental monitoring program, said she’s seeing the same thing.
“We’re seeing an increase in days that exceed 90 degrees F. and we’re seeing an increase in the nighttime temperatures,” she said.
Some of this is just due to normal summer weather patterns.
Jacquemin said the jet stream — the upper atmosphere’s changeable river of air — has now created a Bermuda high, a stalled high pressure system in the Atlantic Ocean that pumps a steady flow of heat and humidity toward the Northeast.
But Mitch Wagener, professor of biology at Western, pointed out that the recent Women’s World Cup soccer matches in France involved all-out effort in sweltering temperatures.
“It’s been 90 degrees in Western Europe,” Wagener said.
Which is where climate change enters the picture.
As the climate warms, it evaporates more water creating more humidity. Air with more moisture retains more heat. During the recent, brutal hot spell, the heat index — heat plus humidity — topped 100 degrees
But climate change is happening because of an increase in the levels of greenhouse gases — especially carbon dioxide — in the atmosphere. Wagener said the increased levels of CO2 help hold the heat in place at night.
“It doesn’t radiate back into the atmosphere,” he said.
These higher temperatures have a variety of implications, none of them particularly good.
They mean more misery for people without air conditioning, especially in urban settings where the asphalt and concrete absorb heat and release it slowly. Environmentalists refer to them as heat traps.
Higher temperatures mean higher energy demands because of all the air conditioners that are turned on. That, in turn, means more pressure on the electric grid delivering the electricity to run those air conditioners and more pollution — a byproduct of creating more energy.
It means unhealthier air — high temperatures reacting with nitrogen oxides from automobile exhaust creates ground level ozone — aka smog. That can aggravate pulmonary and heart problems and trigger asthma attacks.
Paul Ferrell, assistant director of air planning for the state Department of Energy and Environmental Protection, said that so far this year there have been 11 bad air alert days in the state in 2019 — six in July, five earlier in the year.
In 2018, he said, there were 22 such days.
“It all depends on the temperature,” Farrell said. Cool summers keep bad air days in check. Hot summers produce 20 or more.
But ozone levels aside, high temperatures are hard on people. With higher evening temperatures, people without air conditioners simply don’t get a chance to cool off.
“Heat of and by itself is a serious health risk,” Farrell said.
It can also be hard on non-humans.
Margaret Miner, consultant to the Rivers Alliance of Connecticut, said that when the temperature rises, rivers and lakes heat up. In some Connecticut rivers — already made more shallow by diminished summer stream flows — that heating can penetrate through the entire water column.
Fish can escape to cooler water, pools where trees shade the streams or where smaller brooks enter rivers, bringing a supply of cool, fresh water.
But that’s no guarantee of survival. Miner said during the state’s last drought, she saw such pools get so crowded with fish that some got pushed to the edges where they died in the heat.
She said it also isn’t great for aquatic life in general. Cold water species in Long Island Sound, for example, may be leaving as the water there warms.
“It effects the entire ecological system,” she said.