Climate expert: Summer heat is here to stay

PULLMAN — No one argues that it wasn’t hot during the summer of 2021.

“There was an all-time high temperature record set in Washington State this summer,” said Nicholas Bond, Washington State Climatologist and a researcher at the University of Washington.

Temperature gauges in the state’s AgWeatherNet recorded a lot of temperatures of 116, 117 and 118 Fahrenheit across Central and Eastern Washington in late June and early July 2021, Bond said, as he described the summer’s heat wave during the introductory address for Washington State University’s Weather School 2022, held virtually Feb. 4.

“At one place in the Hanford Site, there’s good evidence that it hit 120, an all-time state record,” he added.

There’s a link between global climate change — rising temperatures across the world — and heat waves like the one Washington state experienced last summer, Bond said. It’s not a tight relationship, he added, but hotter average temperatures do generally lead to increased prevalence of heat waves.

“Basically, global warming made that heatwave that much more likely to happen and made it that much more intense, something like two degrees celsius, almost four degree Fahrenheit, hotter than it otherwise would have been,” Bond said.

Because of that continued warming, which scientific consensus attributes to increased levels of greenhouse gasses like carbon dioxide and methane brought about by the industrial revolution and intensive agriculture, Bond said heat waves like last summer’s are going to become a more frequent occurrence.

“In not too far in the future, something like every five or 10 years,” he said.

But it wasn’t just the heat, Bond said. Warmer average global temperatures also mean the air is wetter, containing a lot more water vapor per cubic meter than it used to.

During last summer’s heat wave, Bond said the dew point reached uncomfortable and even dangerous levels.

Dew point is more of an absolute measure of air moisture, and is the temperature at which air will become saturated with water and that water will start to condense to form either dew, frost or fog. Because warmer air can hold more moisture than colder air, it will feel “muggier” on a warmer day even if there is less moisture in the air relative to the temperature.

According to Bond, some of the very hot days during the summer of 2021 heat wave saw dew points in Eastern Washington reaching around 60.

“These kinds of dew points coupled with really high air temperatures, the heat stresses on people doing moderate amounts of activity outside, like agricultural workers, was such that they can work only about 15 minutes out of an hour without suffering heat stroke,” Bond said.

Bond said that in addition to hotter average temperatures and more frequent major heat waves, climate change also means precipitation patterns will change. This will lead to dryer springs and summers and wetter winters where more of the precipitation comes in the form of rain and less as snow.

“With the increase in wintertime being greater than the decrease in summertime, but still more water when we don’t need it as much and less when we really need it,” Bond said.

Bond said one of the risks of hotter weather and more heat waves is the spread to Washington of human, animal and even plant diseases and pests that previously did not find a home here. Citing the example of West Nile Virus, Bond noted that conditions in the last two decades have changed enough so the mosquitoes that carry the disease — which on average kills roughly 20 people each year in California — to gain a foothold in Washington state.

“And it’s not just human health,” he said. “For agriculture, there’s various pests that now are a problem but not maybe a crisis.”

Bond pointed to the potato psyllid, a small insect related to the leafhopper and to aphids, which is now found here during the summer. The insect itself is less the problem than the bacteria it carries that causes zebra chip, a disease that can seriously reduce potato yields.

He also noted that warmer temperatures, including warmer nights, and wetter air would also be a good environment for promoting mildew.

“Are conditions still going to be favorable for wine grapes?” Bond asked. “Turns out, to have high-quality wine grapes, you need the cool nights so they can develop the acids. There are no great Cabernets that come out of Mississippi.”

Charles H. Featherstone can be reached via email at cfeatherstone@columbiabasinherald.com.