Grim 2022 drought outlook for western US offers warnings for future as climate change brings hotter, thirstier atmosphere

Grim 2022 drought outlook for western US offers warnings for future as climate change brings hotter, thirstier atmosphere

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Farmers in some areas are encouraged to preserve and create grasslands that can survive drought and protect the soil. AP Photo/Mark Rogers

Much of the western United States has been plagued by relentless drought since the start of 2020. The drought coincided with record wildfires, intense and long-lasting heat waves, low flows and a dwindling water supply in the reservoirs that millions of people pass through. the region leans.

As summer approaches, the outlook is rather bleak. The National Weather Service’s latest seasonal outlook, released on May 19, 2022, described persistent drought across much of the West and parts of the Great Plains.

One of the drivers of the western drought has been the persistent La Niña conditions in the tropical Pacific since the summer of 2020. During La Niña, cooler tropical Pacific waters help push the jet stream north. This tends to bring fewer storms to the southern United States and produce pronounced drought effects in the southwest.

The other part of the story, and perhaps the most important, is the hotter, thirstier atmosphere caused by a rapidly warming climate.

As a climatologist, I have watched how climate change is increasingly worsening drought conditions, especially in the western and central United States. The past two years have been more than 2 degrees Fahrenheit (1.1 Celsius) warmer than normal in these regions. Large swathes of the southwest were even warmer, with temperatures more than 3 F (1.7 C) higher. Studies suggest the ongoing 20-year drought in the southwest is the most severe in at least 1,200 years, based on soil dryness.

A warmer atmosphere draws more moisture from the ground

A more alcoholic atmosphere tends to draw more water from the earth. It exacerbates evaporative stress on the ground, especially when an area experiences below normal rainfall. High evaporative stress can quickly deplete soil moisture and lead to warmer temperatures because the evaporative cooling effect is diminished. All of this creates hydroclimatic stress for plants, leading to restricted growth, desiccation and even death.

Due to global warming, the southwestern United States has seen an 8% increase in this evaporation demand since the 1980s. This trend is generally occurring in other parts of the country.

The atmosphere at this level transforms what would otherwise be near-normal or moderately dry conditions into more severe or extreme droughts. As the climate warms, increasing atmospheric thirst will continue to intensify water stress, with consequences for water availability, intense and long-lasting heat stress, and large-scale transformation of ecosystems.

Climate models predict ominous prospects of a more arid climate and more severe droughts in the southwest and southern Great Plains over the coming decades.

In addition to the direct impacts of rising temperatures on future droughts, these regions are also expected to experience fewer storms and more days without precipitation. Climate models consistently project a poleward shift in mid-latitude storm tracks this century as the planet warms, which should lead to fewer storms in the southern part of the country.

Expect flash droughts even in the wettest areas

The changing nature of droughts is a concern even in parts of the United States that are expected to experience a sharp increase in annual precipitation during the 21st century. In a warmer future, due to the high evaporative demand on the land, prolonged periods with weeks or months of below normal precipitation in these regions may lead to significant drought, although the general trend is to more precipitation.

Large parts of the northern plains, for example, have seen rainfall increases of 10% or more over the past three decades. However, the region is not immune to severe drought conditions in a warmer climate.

At the end of what was the region’s wettest decade on record, the northern plains experienced an intense flash drought in the summer of 2017 that resulted in agricultural losses of over $2.6 billion and wildfires on millions of acres. Record evaporative demand contributed to the severity of the flash drought, in addition to a severe short-term rainfall deficit. A flash drought is a drought that intensifies rapidly over a period of weeks and often surprises forecasters. The likelihood of flash droughts which can have severe impacts on agriculture and ecosystems and promote large wildfires is expected to increase with a warmer and thirstier atmosphere.

<classe étendue="légende">During the flash drought of 2017, a North Dakota farmer stands in a wheat field that should have been twice as high at the time.</span> <span class="attribution"><une classe="lien " href="https://newsroom.ap.org/detail/PlainsDrought/6fbb416f8e92416cbf1ea37fef567c9c/photo" rel="nofollow noopener" cible="_Vide" data-ylk ="slk:AP Photo/Blake Nicholson">AP Photo/Blake Nicholson</a></span>” data-src=”https://s.yimg.com/ny/api/res/1.2/4MRbEws_pRtt1QBrAqDZbw–/YXBwaWQ9aGlnaGxhbmRlcjt3PTcwNQ–/https://s.yimg.com/uu/api/res/1.2/ FYBDv69qTPQesHaLlgQl.w–~B/aD0wO3c9MDthcHBpZD15dGFjaHlvbg–/https://media.zenfs.com/en/the_conversation_us_articles_815/26c8f8c1e1f22718a5261a071fdf2802″/><noscript><img alt=During the flash drought of 2017, a North Dakota farmer stands in a wheat field that should have been twice as high at the time. AP Photo/Blake Nicholson” src=”https://s.yimg.com/ny/api/res/1.2/4MRbEws_pRtt1QBrAqDZbw–/YXBwaWQ9aGlnaGxhbmRlcjt3PTcwNQ–/https://s.yimg.com/uu/api/res/1.2/FYBDv69qTPQesHaLlgQl. w–~B/aD0wO3c9MDthcHBpZD15dGFjaHlvbg–/https://media.zenfs.com/en/the_conversation_us_articles_815/26c8f8c1e1f22718a5261a071fdf2802″ class=”caas-img”/>
During the flash drought of 2017, a North Dakota farmer stands in a wheat field that should have been twice as high at the time. AP Photo/Blake Nicholson

Flash droughts are also becoming a growing concern in the northeast. In 2020, much of New England experienced extreme hydrological drought, with low groundwater flows and levels and widespread crop losses between May and September. Aided by very hot and dry weather conditions, the drought developed very rapidly during this period from above normal wet conditions.

As humanity moves into a warmer future, prolonged periods of weeks to months of below normal rainfall are going to be of greater concern almost everywhere.

On the way to unknown territory

Other forms of drought also appear.

Atmospheric warming causes snow droughts because more precipitation falls as rain rather than snow and the snow melts earlier. Shorter snow seasons and longer growing seasons due to warmer temperatures are changing the timing of ecological responses.

<classe étendue="légende"> The tub ring on Lake Powell, one of the nation’s largest reservoirs, bears witness to the decline in its water level during two decades of drought in Arizona.  The Colorado River Reservoir is crucial for water supply and hydroelectricity.</span> <span class="attribution"><une classe="lien " href="https://www.gettyimages.com/detail/news-photo/the-tall-bleached-bathtub-ring-is-visible-on-the-rocky-news-photo/1325430487" rel="nofollow noopener" cible="_Vide" data-ylk ="slk:Justin Sullivan/Getty Images">Justin Sullivan/Getty Images</a></span>” data-src=”https://s.yimg.com/ny/api/res/1.2/82UYDkBEp3OxPWUph.M_ow–/YXBwaWQ9aGlnaGxhbmRlcjt3PTcwNQ–/https://s.yimg.com/uu/api/res/ 1.2/Tu0wTQh.jWcRfoUH3BuPMA–~B/aD0wO3c9MDthcHBpZD15dGFjaHlvbg–/https://media.zenfs.com/en/the_conversation_us_articles_815/cbef4a584fed0232de95034474d4dc3b”/><noscript><img alt= The tub ring on Lake Powell, one of the nation’s largest reservoirs, bears witness to the decline in its water level during two decades of drought in Arizona. The Colorado River Reservoir is crucial for water supply and hydroelectricity. Justin Sullivan/Getty Images” src=”https://s.yimg.com/ny/api/res/1.2/82UYDkBEp3OxPWUph.M_ow–/YXBwaWQ9aGlnaGxhbmRlcjt3PTcwNQ–/https://s.yimg.com/uu/api/res/1.2/ Tu0wTQh.jWcRfoUH3BuPMA–~B/aD0wO3c9MDthcHBpZD15dGFjaHlvbg–/https://media.zenfs.com/en/the_conversation_us_articles_815/cbef4a584fed0232de95034474d4dc3b” class=”caas-img”/>
The tub ring of Lake Powell, one of the nation’s largest reservoirs, bears witness to the decline in its water level during two decades of drought in Arizona. The Colorado River Reservoir is crucial for water supply and hydroelectricity. Justin Sullivan/Getty Images

Land greens earlier and leads to earlier water loss from the land surface through evapotranspiration – the loss of water from plants and soil. This could result in drier soils in the second half of the growing season. As a result, parts of the central and western United States may see both increased greening and drying in the future, separated seasonally throughout the growing season.

With a rapidly changing climate, we are entering uncharted territory. The world will need new ways to better anticipate future droughts that could transform natural and human systems.

Read more: The future of hydroelectricity is clouded by droughts, floods and climate change – it is also essential for the American electric grid

This article is republished from The Conversation, a nonprofit news site dedicated to sharing ideas from academic experts. It was written by: Imtiaz Rangwala, University of Colorado Boulder.

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Imtiaz Rangwala receives funding from the USGS, USDA, NOAA and the US Forest Service. He is affiliated with the University of Colorado at Boulder, the North Central Climate Adaptation Science Center, and Western Water Assessment.

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