Heat wave hits western US 1:27
With more than 300 temperature records at risk this week, more than an eighth of the United States population - more than 40 million people - are on alert across the west of the country for a lasting heat wave. and potentially lethal.
"There is no easy way to say this, so let's get straight to the point: it's going to be * very * hot for a * long time *," tweeted the National Weather Service in Salt Lake City in anticipation of this historic heat wave. .
According to experts, this heat wave and the exceptional drought in the southwest of the country are part of a damaging loop fueled by climate change.
The hotter, the drier;
the drier, the hotter.
"When it comes to extreme weather events, climate change works against us," Katharine Hayhoe, climate researcher and chief scientist at the Nature Conservancy, told CNN Weather in an email.
"We always have the possibility of extreme heat, especially in summer: but as the world warms, we see that summer heat waves arrive earlier, last longer, and become hotter and more intense."
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The southwest is trapped under a dome of heat
On Tuesday, Salt Lake City recorded its third consecutive day of hot weather above 37 ° C, setting daily and all-time records.
The city reached a maximum temperature of 41.6 ° C on Tuesday afternoon, tying its all-time high, previously reached in July.
For perspective, records in Salt Lake City date back to 1874. In that time, more than 50,000 calendar days of temperatures have been observed.
Tuesday is the third time the city has reached 41.6 ° C, which is a 1-in-50-year event.
[5:43 PM] 107 ° F.
We have now tied the highest temperature EVER recorded at Salt Lake City in any month of the year, in the last 147 years of records.
It has only happened twice before: July 2002 and July 1960. #utwx pic.twitter.com/lySLjV748q
- NWS Salt Lake City (@NWSSaltLakeCity) June 15, 2021
The cause is a huge high pressure ridge, commonly known as a heat dome, that is rapidly gaining strength over the western United States.
A combination of falling air, clear skies and prolonged solar radiation will cause temperatures this week to be between 5.5 ° C and 13 ° C above the expected values for the season.
This ridge is also responsible for the relentless drought, as it drives rain away from the region.
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In a heat dome, the high pressures act like a lid on the atmosphere and when hot air tries to escape, the lid forces it back down, heating up even more as it sinks.
"The hotter it gets, the stronger the ridge," Hayhoe said.
"So even if climate change is not responsible for the formation of the ridge, it can make it last longer and stronger than it would be otherwise, making the drought more intense and longer lasting."
Amid a historic drought and the lowest water level on record in nearby Lake Mead, the state of Nevada will also challenge its all-time record for maximum temperatures this week, currently held by the City of Laughlin, which reached 51.6. ° C on June 29, 1994. Highs in Laughlin are expected to range between 48.8 ° C and 50 ° C from Wednesday to Sunday;
the average at this time of year is 41.1 ° C.
Widespread records of temperatures above 37.7 ° C are being seen in regions as far north as Idaho and Montana.
On Tuesday, Billings, Montana, hit 40.5 ° C, equaling the hottest weather ever recorded in June and erasing the daily record of 36.6 ° C, held for more than 30 years.
As the week progresses, so does the long-lasting heat wave.
More records in danger of being broken
On Wednesday afternoon, the city of Las Vegas will brush with history as maximum temperatures are forecast to reach 46.6 ° C, less than one degree from the city's all-time record of 47.2 ° C.
This mark has only been reached four times since records began in 1937.
Not far from there, in Phoenix, where residents are well used to sweltering heat, the temperature is expected to be impressive even by their standards.
The maximums at this time of year are usually around 40.5 ° C degrees.
Typically, the first day average of 46.1 ° comes during the first week of July.
However, four days before the official arrival of summer, highs in Phoenix soared to a record 46.1 ° C on Tuesday.
The heat wave will continue until the end of the week.
In fact, forecasting models indicate that they can reach or exceed 46.1 ° C every day from Wednesday to Friday.
This would tie Phoenix's all-time record for the most consecutive days of 46.1 ° C with four days.
Perhaps not surprisingly, in the summer of 2020, the city reached 46.1 ° C on four successive days on two separate occasions.
In the US, five of the 10 warmest years on record have occurred since 2012, and the overall trend indicates little change.
There have always been heat waves, but they are getting worse
There have always been heat waves, droughts, wildfires, and more, long before humans began to change the climate.
What scientists are beginning to say, Hayhoe explains, is how much climate change worsens these phenomena.
"Scientists are beginning to be able to say 'a lot!'
and even to answer this question with numbers for specific events, "he said.
"For example, scientists have found that climate change made the 2019 European heat wave 10 times more likely, and the June 2020 Siberian heat wave 600 times more likely."
What is happening in Siberia, where there was an unprecedented heat wave?
In the future, heat waves and drought are likely to worsen, Hayhoe said.
Especially in areas that are already at natural risk of drought.
Ironically, climate change will also make heavy rain events more frequent.
"Which is not good news, either," explains Hayhoe.
"It can be damaging, making it difficult to replenish depleted groundwater and groundwater during a drought when rain falls in heavy downpours, as most of it escapes."
The future looks different than the records of the past.
"We can no longer rely on the past as a reliable predictor of future conditions, as we have for hundreds and even thousands of years," Hayhoe said.
"Instead, we must prepare for hotter conditions and more damaging droughts than we have seen so far."
Climate change Heat wave Drought