The numbers explain how and why West cooks, burns and dries

The American West bakes, burns and dries in intertwined extreme weather conditions. Four sets of numbers explain how bad it is now, while several more explain why it has become so bad.

The West is going through “the winning trifecta of an epic year of drought followed by unbelievable heat over the past two months and now we have fires,” said John Abatzoglou, University climate and fire specialist of California Merced. “It’s a story of cascading impacts. “

And that of climate change, the data show.

SAVE THE HEAT

In the past 30 days, the country has set 585 all-time heat records, according to the National Oceanic and Atmospheric Administration. Of these, 349 are high daily temperatures and 236 are the hottest overnight temperatures, which are vital for people to recover from deadly heat waves.

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And that doesn’t include Death Valley hitting 130 degrees (54 degrees Celsius) beforehand. If confirmed, it would be the hottest temperature on Earth in decades – and several meteorologists say it would be the hottest reliable temperature on record because many don’t trust the accuracy of two hotter records.

Another part of Death Valley likely set the world record on July 11 for hottest 24 hour period averaging the daily maximum and the overnight minimum to reach 118.1 (47.9 degrees Celsius), according to meteorologist Maximiliano Herrera, who tracks extreme weather conditions.

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The average daily maximum temperature for the entire region from the Rockies and westward in June was 85.7 degrees (29.8 degrees Celsius), which broke the old record of 1.3 degrees (0.7 degrees Celsius), according to NOAA.

SEVERE DROUGHT

According to the University of Nebraska Drought Monitor, nearly 60% of the western United States is considered exceptional or extreme drought, the two highest categories. This is the highest percentage in the 20 years that the Drought Monitor has tracked. Less than 1% of the West is not drought or considered unusually dry, a record as well.

LOW SOIL MOISTURE

The amount of moisture in the soil is essential, as normally part of the sun’s energy is used to evaporate moisture from the soil and plants. Additionally, when the soil and plants are dry, areas burn much more often and hotter in wildfires and the available water supply decreases for places like California, a “real indicator of how dry things are. “said Abatzoglou.

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NOAA and NASA show soil moisture levels are among the lowest on record for much of the West. Most areas of California, Oregon, Washington, Nevada, Arizona, Utah, and Idaho are drier than 99% in other years.

THE FIRES OF NATURE BURN

According to the National Interagency Fire Center, 68 large active fires are burning, consuming 1,038,003 acres (420,000 hectares) of land. With these fires and those in Canada, there is “a large area of ​​smoke over much of the United States and Canada,” NOAA said Tuesday.

So far this year, wildfires have burned 2.2 million acres (899,000 hectares), which is below the 10-year average for this time of year. But that may change as dry plants are at a very high risk of burning in much of the West, as shown by what experts call the energy-releasing component of fire.

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HOW WE ARE HERE

“The history of the heat wave cannot be seen as an isolated extreme event, but rather as part of a longer history of climate change with more related, more extensive and varied impacts,” said the climatologist Jennifer Francis of the Woodwell Climate Research Center in Cape Cod.

SUMMERS BECOME WARMER

From 1991 to 2020, summers in the Rockies and westward on average became 2.7 degrees (1.5 Celsius) warmer. The West is warming faster than the rest of the United States and the globe.

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MORE DMES OF LOWER JET FLOW HEAT

The weather phenomenon now roasting the West that brought temperatures of 116 degrees (46.7 Celsius) to Portland, Oregon at the end of June is often referred to as a thermal dome – where the high pressure parks. over an area and hot air flows. This usually happens when the jet stream – the river of air that brings weather to certain places – gets stuck and doesn’t push storms forward.

Pennsylvania State University climatologist Michael Mann found that the number of jet stream stalls in the northern hemisphere increased from about six times per summer in the early 1980s to about eight times per summer. now.

“We have shown that climate change is making these blocked summer jets more common,” Mann said.

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LESS RAIN

The West received an average of 13.6 inches (34.5 centimeters) of snow and rain from July 2020 to June 2021. Over the past 10 years, the region has received on average just over 19 inches (48 centimeters) of precipitation per year amid what scientists call a mega-drought. In the 1980s and 1990s, before the onset of the mega-drought, the West received on average nearly 22 inches (56 centimeters) of rain.

A 2020 study said that “global warming has pushed what would have been a moderate drought in southwestern North America into mega-drought territory.”

MORE FIRES OF NATURE

From 2011 to 2020, an average of 7.5 million acres (3 million hectares) burned in forest fires each year. That’s more than double the average of 3.6 million acres (1.4 million hectares) per year from 1991 to 2000, according to data from the National Interagency Fire Center.

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It’s not just more acres burned, but more “really, really big fires,” UC Merced’s Abatzoglou said, noting that the combination of drought and heat means the plants are more likely to burn and fires to get bigger.

“The drought we have experienced this year and the warm temperatures allowed the fire season to unfold harshly and really, very early,” he said.

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Follow Seth Borenstein on Twitter at @borenbears.

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