The West Coast is burning up. Death Valley’s average temperature in July –107.4 degrees Fahrenheit — was the hottest on record, and cities like Seattle, Portland, Salt Lake City, Palm Springs and Phoenix have reached record scorching temps over the past few weeks, too. Meanwhile, wildfires are raging north of the border in British Columbia and Cascade Mountains.
Here’s why things are so toasty right now.
Climate change might be tipping records. “A few of our temperature records would not have been broken with this heat wave,” Philip Mote, a climate scientist at Oregon State University, said. “If you took this specific meteorological condition and then dialed back the greenhouse gases to what they were 50 years ago, it would be a little bit cooler. Portland instead of being 103 yesterday might’ve only been 101.” Weather experts shared the sentiment that climate change’s contribution to an event like this “might be a degree or two.” Without global warming, there would still be a heat wave, just probably not a record-setting one.
Wildfire haze might be…a good thing? Wildfires in British Columbia and the Cascade mountains could be lowering temps, slightly. Wildfire haze has drifted into Seattle and Portland. The haze likely cools temperatures by reflecting sunlight back into the atmosphere, David Bishop, a meteorologist with the National Weather Service in Portland, Oregon, said. That keeps the city from taking on additional heat. But haze’s contribution to the heat wave in the northwest is likely minimal, Mote noted.
— NWS Seattle (@NWSSeattle) August 2, 2017
Weather is weird. “Every extreme weather event is something the atmosphere does every once in awhile,” Mote said. Clifford Mass, an atmospheric scientist at the University of Washington, agreed. For any heat wave, most of it has to be natural because it’s associated with changes in the circulation of the atmosphere, he said.
Also, it’s summer. Even in Death Valley and the Pacific Northwest, summertime means warmer temps. “Typically when high pressure moves over an area that warms up temps on the surface, so that’s not an unusual event to happen,” Bishop said. “What’s happening in this case, it’s staying over the area.” Along with minimal rainfall, the high pressure itself increases the potential for extremely high temperatures, Bishop said.
But, things will only get hotter and hotter. “There’s pretty clear evidence that if you pick any extreme temperature, it’s been exceeded more often in recent years,” Mote said. This is particularly true for nighttime lows, which have become much hotter in the last few decades, according to a recent study. The simple addition of heat to the system helps it get hotter more often, Mote said.