HEAT

soil, but scientists say the Western soil is so dry that instead that energy makes the air even warmer.

“When the soil is wet, heat waves aren’t so bad,” said Williams, who has calculated that soil in the western half of the nation is the driest it has been since 1895. “But if it’s dry, we are under extreme risk.”

HOW DO RECENT WILDFIRES FIGURE INTO THIS?

Scientists say the wildfires that have erupted in recent days have been fed by the excessive heat across the region. Climate change contributes to the drought conditions and makes trees and shrubs more likely to catch fire.

At least 14 new wildfires broke out this week in Montana and Wyoming as the record heat sparked an early start to the fire season. Firefighters also battled blazes in Arizona and New Mexico.

“From a fire potential standpoint, what is capable this year, it is certainly much more severe than we’ve seen in the past,” U.S. Department of Agriculture fire meteorologist Gina Palma said in a climate briefing Thursday.

Palma said the drought-related fire risks were especially pronounced in higher elevations across much of the U.S. West, from the Rocky

Mountains down into the Southwest and parts of California.

“You will be seeing very extreme fire behavior, certainly conditions that we would not normally see in June,” she said.

IS THIS THE NEW NORMAL?

A growing number of scientific studies are concluding that heat waves in some cases can be directly attributed to climate change, said Kristie L. Ebi, a professor at the Center for Health and the Global Environment at the University of Washington.

That means the U.S. West and the rest of the world can expect more extreme heat waves in the future unless officials move to cut down on greenhouse gas emissions, Ebi and other scientists say.

A study last month estimated the percent and number of heat deaths each year that can be attributed to human-caused climate change. It included about 200 U.S. cities and found more than 1,100 deaths a year from climate changecaused heat, representing about 35% of all heat deaths in the country.

On average each year, Phoenix has 23 climate-triggered heat deaths, Los Angeles has 21 and Tucson has 13, the study said.

“Climate change is harming us now,” Ebi said. “It’s a future problem, but it’s also a current problem.”