Climate graphic of the week: US heat and drought coincide with historic climate bill

The most severe heatwaves in the US Pacific Northwest since the deadly 2021 records were set, and drought in almost half of the country, provided the backdrop to the historic $369bn bill to tackle energy security and climate change this week.

Increasing soil dryness has helped to fuel the heat, as the air heats more quickly without moisture in the ground to evaporate and cool the atmosphere. This could have the effect of boosting temperatures up to 6.5C (20F) above average, said AccuWeather, the US commercial weather service.

While the temperatures in parts of Oregon and Washington states fell short of all-time records set in the late June 2021 heatwave, it said, the past week’s heat had greater staying power.

The National Weather Service in Portland forecast the scorching temperatures would persist through the weekend, and the region was predicted to break duration records for heatwaves.

Portland hit a new daily record high of 38.9C at the start of the week and was on track to equal its longest streak of six consecutive days of 35C (95F) or higher, with excessive weather warnings for the Willamette Valley and Columbia River Gorge areas of Oregon. Seattle also reported a new record daily high of 34.4C (94F) this week.

Heat wave set to continue across the US.  Animated map of US showing maximum temperature from July 28 to August 2

The Nasa Earth Observatory has reported that by the end of June almost half of the US was in “moderate to extreme drought”, based on its analyzes of soil conditions and use of mapping tools.

California experienced its driest January, February and March on record in 2022, the agency said, as nearly all of the state fell into “severe to extreme drought”.

Droughts are complex events that cannot always be attributed directly to climate change, according to a recent paper by scientists who specialize in the subject of weather attribution.

In some areas, however, changing rain patterns, such as short bursts of very heavy rain, might contribute to a “worsening of droughts,” the study concluded.

“The fingerprint of climate change on increasing drought has been observed in several drought-prone regions of the world,” it said. “This is largely due to amplified temperatures driving evaporation and melting snowpack, reducing the meltwater contribution to river flows.”

Newly released data from NASA’s Landsat program in 2000 and 2022 show the dramatic effects of the drought that has extended to the southwestern US and driven water levels to just 27 percent of its capacity. The depleted water levels have exposed human remains in recent months.

US megadrought map

Images of Lake Mead and Lake Powell, critical reservoirs on the Colorado River feeding the Hoover Dam, provide “a stark illustration of climate change and a long-term drought that may be the worst in the US West in 12 centuries”, NASA wrote.

Additional reporting by Camilla Hodgson

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