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2024-12-22 10:50:16 [探索] 来源：有聲有色網

Climate 101is a Mashable series that answers provoking and salient questions about Earth’s warming climate.

Records will break. Some will get smashed.

A dangerous heat wave will blanket Washington, Oregon, Northern California, British Columbia, and beyond, lasting this weekend through early next week. A pattern of unusually hot air will settle over the region, and (like any heat wave today) it will be amplified by human-caused climate change, with an added kick from serious Western drought.

That's why Portland, for example, expects to easily top, if not obliterate, its warmest June day on record and challenge its all-time record of 107 degrees Fahrenheit. For the region, temperatures will be oppressive.

"We're going to see temperatures way, way, way above normal across the Pacific Northwest," said Dave Lawrence, a meteorologist with the National Weather Service.

"There's a lot more vulnerability."

The looming problem is many of these areas don't usually get so hot. People, and the buildings they live in, can be ill-prepared for this type of extreme heat. "There's a lot more vulnerability," explained Lawrence. Among weather events in the U.S., heat waves kill the most people.

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Heat waves are a nexus of weather and climate. These are the primary ingredients for this extreme event:

1. Heat dome: The hot weather settling over the region is called a "heat dome," "ridge," or a "high pressure system." Essentially, a mass of warm air is getting stuck over a large portion of the Western U.S., as other weather systems (like in Alaska and Canada) lock it in place in the atmosphere. It's not going to just briefly pass through. "It's a stagnant weather pattern," explained Lawrence.

What's more, in these high-pressure weather environments, air heats up as it sinks toward the surface, contributing to even higher temperatures.

2. Climate change: Earth's climate is relentlessly warming. Globally, it's around 2 F warmer than it was in the late 1800s, though certain regions (particularly in the West), have heated up significantly more than other places.

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"The whole planet is hotter, so temperatures in the middle of that heat ridge are also hotter," explained Jack Scheff, a climate scientist at the University of North Carolina at Charlotte.

"Climate change is making extreme heat waves even more extreme and common."

Research has repeatedly shown that boosted global temperatures amplify heat waves, making them more severe, explained Daniel Swain, a climate scientist at UCLA and the National Center for Atmospheric Research.

"Climate change is making extreme heat waves even more extreme and common," Swain emphasized.

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3. Drought:

Nearly all of the Western U.S. is mired in drought, some of it extreme and exceptional. Drought means dry soil, which intensifies heat during heat waves. When there's moisture in the ground, some of the sun's energy goes toward evaporating this water. But when it's dry, "That sunlight goes directly into heating the ground and air," explained Scheff.

"Almost everyone agrees that if you have drought in place, heat waves will be stronger," Scheff added.

Meteorologists, and their impressively accurate and improving weather models, account for soil conditions when making forecasts. This is another reason why temperatures are forecast to get so high. About 80 percent of the Pacific Northwest is in drought. "The soils are just baked," said the National Weather Service's Lawrence.

Heat and drought can feed each other.

"Drought and heat are natural dance partners," NOAA meteorologist Tom Di Liberto recently wrote, when describing another Western heat wave earlier this month. "Drought conditions are made more likely or more extreme when temperatures soar. And vice versa, hot temperatures can be made even hotter by a drought-stricken landscape."