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Explained: What is megadrought that is gripping the American West?

Explained: What is megadrought that is gripping the American West?
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By CNBCTV18.com Feb 16, 2022 7:59:36 PM IST (Published)

Researchers believe climate change is the principal driver of the present megadrought in southwestern US, believed to be the worst in 1200 years, and warned that multi-decade periods of dryness will only increase over the rest of the century -- unless better sense prevails.

The American West has been locked in an extreme megadrought in the last two decades, experiencing what scientists believe are the driest 20 years in the region in at least 1,200 years.

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In a study published on February 14 in the journal, Nature Climate Change, researchers said human-caused climate change is the principal driver of the present condition and warned of even drier decades in the future.

The researchers attributed 42 percent of the severity to higher temperatures as a direct result of greenhouse gas emissions trapping the heat in the atmosphere.

According to the researchers, drought conditions in southwestern North America during this century are more severe than the megadrought in the late 1500s.

What is a megadrought?

The National Oceanic and Atmospheric Administration (NOAA) defines a megadrought as a prolonged and severe drought spanning over a period of two decades or longer.

Over the centuries, megadroughts have lasted for decades. In the second century, the megadrought lasted for 50 years, while those occurring in the 9th, 12th, 13th and 16th centuries remained for a period of 30-40 years.

There may be a brief respite from the dryness within that period with occasional wet years, but the dryness retains a long-term grip.

In the Southwest, places such as Utah, Arizona, Nevada, parts of California, Colorado and New Mexico have experienced such conditions in the last two decades. Much of the southwestern region is classified as a desert, where normal weather is classified by high heat, low humidity and little precipitation.

In the winter of 2016-17, huge storms hit California, and in 2019, Arizona received rains in the spring season. However, the respite was brief, The New York Times reported.

“Rather than starting to die away after wet years in 2017 and 2019, the 2000s drought has ramped up with authority in 2020-2021,” CNBC quoted A. Park Williams, climate scientist at UCLA who led the analysis, as saying. Williams said there were no signs of the 2000s drought starting to relent.

What is happening now?

The US drought monitor revealed that nearly 65 percent of the American West was experiencing severe drought conditions, intense wildfires and declining water supplies, The Guardian reported.

In summer 2021, the two largest reservoirs in the country -- Lake Mead and Lake Powell --saw water levels receding to their lowest ever recorded.

In 2020, more than 10 million acres of land in the US was burned down in the severe wildfires.

Last year, federal officials had to order water cuts for the first time in the Colorado River Basin, which affected water and power supplies to more than 40 million people.

According to experts, the study is a call to gear up for the future. Although measures have been taken to better manage the crisis, “climate change is outpacing us,” The Guardian quoted Alvar Escriva-Bou, a senior fellow at the Public Policy Institute of California’s Water Policy Center, as saying.

Jason Smerdon, a climate scientist at Columbia University, who also worked on the study, warned that the “multi-decade periods of dryness will only increase with the rest of the century.”

However, Smerdon is hopeful that the extreme events may spur people’s understanding and action to better the situation.

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