A wave of "severe drought" sweeps the United States and warnings to continue until 2030

It is unlikely that the freeze caused by a drought of this magnitude will be broken in a year that happens to rain well, and it will take a few years of high humidity to make up for that shortfall.

Drought in the United States Source: French

A wave of drought threatens the southwest of the United States of America, and warnings of the impact of global warming in increasing the severity of drought and water scarcity for millions of people as a result of an increase in temperatures by two degrees Celsius above pre-industrial levels.

A new study published on February 14 in the journal Nature Climate Change shows that global warming has made droughts in the southwest of the United States more severe by 40% since AD ​​800.

The study team from Columbia University and the University of California expects this drought to continue until 2030.

Soil moisture at its lowest

According to a report published in Science Alert, Brad Udall, a climatologist at Colorado State University, believes that soil moisture is an important indicator for assessing drought, as it is "the reservoir on which life depends."

However, hot and dry air absorbs moisture from the soil and leads to its drying unless it is nourished by rain and snow water. Recent research has shown that rivers and streams flow less in years of low soil moisture, which is a problem for farmers in areas fed by the Colorado River and other waterways across the west, which have seen a marked decline in flow rates in recent years.

Park Williams, a climate scientist at the University of California, Los Angeles, and his team wanted to understand how severe the current drought is compared to past events across the Southwest from northern Mexico to Idaho. By 2020, Williams' team published a study that investigated regional droughts over a period of 1,200 years, based on a record of data that relied mainly on analysis of tree growth patterns there.

The researchers made the trees an archive that records historical changes in temperature, precipitation and other information related to the climate. This is because trees adapt to the weather and climate in their rings, so layers of new wood are thicker in years when moisture is plentiful, and in return, the rings are thin and small in size in years of drought and extreme heat.

Soil moisture map

In 2020, the team was able to create a soil moisture map after reading the rings of more than 1,500 trees across the western United States. Williams and his colleagues reported 40 droughts between 800 and 2018, 4 of which were exceptionally severe. .

According to a report published on the National Geographic website, the years 2020 and 2021 recorded the highest values ​​of drought, as the summer of 2021 witnessed unprecedented heat waves that sucked any trace of moisture from the soil to the extent that many farmers were unable to irrigate their crops as required of water.

Thus, meager water levels along the Colorado River have forced mandatory cuts in the amount of water that can go to states like Arizona and Nevada.

In their latest study, Williams and his colleagues added these last years to their analysis, and it turns out that the current drought is the most severe but not the longest yet, given that many previous mega droughts have lasted longer.

Exacerbation of severe droughts

The researchers found that climate change made the atmosphere hotter and drier, and resulted in approximately 42% of soil drying out between 2000-2021, making 2021 alone 20% drier than expected without the impact of climate change.

It is estimated that climate change has caused about half of the losses related to the flow rates of the Colorado River in recent years, a huge impact with serious global consequences. We are currently observing a renegotiation of the amount of water available to states that depend on the Colorado River and a reassessment of their water plans.

According to the National Geographic website, global temperatures have risen by 1.1 degrees Celsius since the late 19th century and are expected to rise further in the coming decades unless governments make rapid and decisive cuts in greenhouse gas emissions.

When does the drought end?

The problem is that the current climate is much hotter than before and is also associated with large and continuous droughts over many years, and thus it will be difficult to compensate for the lack of soil moisture caused by more than 20 years of drought.

“It is unlikely that the deadlock caused by a drought of this magnitude will be broken in a year that happens to rain well,” Williams says. “It would take a few years of high humidity to make up for that shortfall."

To assess the region's likelihood of emerging from that drought in the next few years, the study team examined wet and dry patterns over a 40-year time period along their 1,200-year time record, then projected those historical patterns onto the current state to estimate the likelihood that the drought would continue for another year, two or more. more.

The researchers concluded that - in the absence of climate change - there is a high probability of 94% that drought will continue until 2023, and with a 33% probability that drought will continue until 2030.

According to a report published by France 24, the draft report of the Intergovernmental Panel on Climate Change- IPCC, consisting of 4,000 pages on climate impacts, expected that 800 million to 3 billion people would suffer from water shortage in the long term. Due to the drought caused by global warming of two degrees Celsius above pre-industrial levels.