Drought in southwestern United States, worst in century, linked by NOAA to climate change

During the same period, from January 2020 to August 2021, the region also experienced the third highest daily average temperatures measured since record keeping began in the late 19th century, according to the Drought Task of the National Oceanic and Atmospheric Administration (NOAA). Obligate.

Reuters reports that the study warned that conditions of extreme drought are likely to worsen and repeat themselves “until rigorous climate mitigation is continued and regional warming trends are reversed.”

Drought began in early 2020 in California, Nevada and the Four Corners states of Arizona, Utah, Colorado, and New Mexico and resulted in unprecedented water shortages in reservoirs in the region, while fueling devastating wildfires in the west over the past two years. noted the report.

The study also cited declining reservoir levels that threatened or disrupted drinking water supplies, irrigation systems, hydropower production, agriculture, fishing and recreation, with losses. immediate economic billions of dollars.

Much of the below normal winter precipitation was likely due to natural weather variations, including a La Nina model, while research suggests successive summers of low monsoon precipitation can also occur by chance, according to the report. from NOAA.

However, unusually high temperatures coinciding with the southwest’s historic drought are symptomatic of man-made climate change and have intensified the drought, making it “more impactful” in several ways, the report’s authors concluded.

Higher than normal heat helps dry out surface and soil moisture and reduces snowfall in winter, which in turn decreases storage of dry season surface water from snowmelt runoff , according to the report.

A weak snowpack and parched soil can also create an “earth-atmosphere feedback” that worsens a drought by helping to raise soil temperatures while leaving less moisture available to evaporate for future precipitation, according to the study.

Extremely high temperatures also greatly increase the demand for water, further straining depleted reservoirs and rivers.

The report noted that the drought was so severe that states sharing the Colorado River, the region’s main river basin, experienced the first-ever water shortages.

The report focuses on drought in six states in the American Southwest, which are home to more than 60 million people, but its implications extend beyond that region, the authors said.

“Half of the United States is experiencing unprecedented drought, precisely as the country’s economy struggles to emerge from the effects of COVID,” senior author and Dartmouth College geography professor Justin Mankin said in a statement.

While the summer of 2021 has brought welcome monsoon rains to parts of the southwest, several years of above average rainfall and high elevation snow are needed to replenish the region’s reservoirs, streams and soils. .

“This suggests that for much of the southwestern United States, the current drought will last at least until 2022, potentially longer,” the report said.

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