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Much of the western U.S. has been in the grip of an since early 2020. The dryness has coincided with record-breaking , intense and long-lasting , low stream flows and that millions of people across the region rely on.

Heading into summer, the is pretty grim. The National Weather Service's , issued May 19, 2022, described drought persisting across most of the West and parts of the Great Plains.

One driver of the Western drought has been in the tropical Pacific since the . During La Niña, cooler tropical Pacific waters help nudge the jet stream northward. That tends to bring and produce pronounced drought impacts in the Southwest.

The and perhaps more important part of the story is the .

As a , I've watched how climate change is making drought conditions increasingly worse—particularly in the western and central U.S. The last two years have been more than 2 degrees Fahrenheit (1.1 Celsius) warmer than normal in these regions. Large swaths of the Southwest have been even hotter, with temperatures more than 3 F (1.7 C) higher. is the most severe in at least 1,200 years, based on how dry the soils are.

A hotter atmosphere sucks more moisture from the soil

A thirstier atmosphere tends to extract more water out of the land. It exacerbates on the land, particularly when a region is experiencing below-normal precipitation. High evaporative stress can rapidly deplete soil moisture and lead to hotter temperatures, as the is diminished. All this creates hydroclimatic stress for plants, causing restricted growth, drying and even death.

As a consequence of a warming climate, the U.S. Southwest has seen an 8% increase in this evaporative demand since the 1980s. This trend is generally .

The is turning what would otherwise be near-normal or moderately dry conditions into droughts that are more severe or extreme. As the climate heats up further, the increasing atmospheric thirst will continue to intensify drought stress, with consequences for water availability, long-lasting and intense heat stress, and large-scale ecosystem transformation.

Climate models project ominous prospects of in the Southwest and southern Great Plains in the coming decades.

In addition to direct impacts of increasing temperatures on future droughts, these regions are also expected to see and . Climate models consistently project a during this century as the planet heats up, which is expected to result in fewer storms in the southern tier of the country.

Expect flash droughts even in wetter areas

The changing nature of droughts is a concern in annual precipitation during the 21st century. In a hotter future, because of the high evaporative demand on the land, prolonged periods with weeks to months of below normal precipitation in these areas can lead to significant drought, even if the overall trend is for more precipitation.

Large parts of the northern Plains, for example, have seen precipitation in the last three decades. However, the region is not immune to severe drought conditions in a hotter climate.

At the tail end of what was the on record in the region, the northern Plains experienced that resulted in agricultural losses in excess of $2.6 billion and across millions of acres. contributed to the severity of the flash drought, in addition to a severe short-term precipitation deficit. A flash drought is a drought that and often catches forecasters by surprise. The likelihood of flash droughts that can is expected to with a warmer and thirstier atmosphere.

Flash droughts are also emerging as a growing concern in the Northeast. In 2020, much of New England experienced an , with low stream flows and groundwater levels and widespread crop losses between May and September. Aided by very warm and dry atmospheric conditions, the drought developed very rapidly over that period from what had been above-normal wet conditions.

As humanity enters a hotter future, prolonged periods of weeks to months of below-normal precipitation are going to be of a greater concern almost everywhere.

Heading into unfamiliar territory

Other forms of droughts are also emerging.

Atmospheric heating is causing as more precipitation falls as rain rather than snow and snow melts earlier. Shorter snow seasons and longer growing seasons because of warmer temperatures are .

Land is and causing an earlier loss of water from the land surface through —the loss of water from plants and soil. This could result in drier soils in the latter half of the growing season. As a result, parts of the central and western U.S. could see that are seasonally separated across the growing season.

With a rapidly changing climate, we are entering . The world will need new ways that could transform and human systems.

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