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ALBUQUERQUE — Scientists said Monday that the mega-drought in the Southwest America has become so severe that it’s now the driest twenty years in at least 1200 years in the region, and climate change is largely responsible.

The drought, which began in 2000, has reduced water supplies, devastated farmers and ranchers, and helped fuel forest fires in the region. worst According to researchers, within 500 years.

But the exceptional conditions in the summer of 2021, when nearly two-thirds of the West was in extreme drought, “really went to extremes,” says A. Park Williams, a climate scientist at the University of California, Los Angeles. led an analysis that used tree-ring data to measure drought. As a result, 2000-21 is the driest 22-year period since 800 AD, which goes way back according to the data.

The analysis also showed that human-induced warming played an important role in making the current drought so extreme.

Dr. There will be a drought regardless of climate change, Williams said. “But its severity would only be about 60 percent of what it was.”

Although the findings were not surprising, “the study makes clear how unusual the current conditions are,” said Julie Cole, a climate scientist at the University of Michigan who was not involved in the research.

Dr. Cole said the study also confirms the role of temperature, rather than precipitation, in sustaining extreme droughts. The amount of precipitation may increase or decrease over time and may vary regionally, he said. But as human activities continue to pump greenhouse gases into the atmosphere, temperatures are rising more generally.

Dr. “Air is basically more capable of pulling water from the soil, vegetation, crops, forests,” Cole said. “And it makes drought conditions much more extreme.”

Although there is no uniform definition, mega-drought is generally considered to be both severe and prolonged over several decades. But even in a mega-drought there can be periods of wet conditions. There simply aren’t enough consecutive wet years to end the drought.

This has been the case in the current Western drought with several wet years, especially 2005. Published in the journal Nature Climate Changedetermined that climate change is responsible for the continuation of the current drought after that year.

Dr. “According to our calculations, a little extra dryness in background average conditions caused by human-induced climate change, which basically prevented 2005 from ending the drought event,” Williams said.

The study found that climate change also increases the likelihood that drought will continue. Dr. “This 22-year drought is still in full swing, and this drought is very, very likely to last 23 years,” Williams said.

In the 1,200-year record, the previous few mega-droughts lasted as long as 30 years, according to the researchers. Their analysis concluded that the current drought is likely to last that long. Dr. If it did, it’s almost certain to be drier than the previous 30-year period, Williams said.

Tree rings are a measure of year-to-year growth—wider in rainy years and thinner in dry years. Using observational climate data from the past century, the researchers were able to closely link tree ring width to soil moisture content, a common measure of drought. They then applied this width-moisture relationship to data from much older trees. Dr. Williams said the result was “an almost perfect record of soil moisture” over 12 centuries in the Southwest.

Using this record, the researchers determined that last summer was the second driest year in the last 300 years, and only got drier in the first years of the current drought in 2002.

Monsoon rains in the Southwest desert last summer gave hope that drought could end, as did heavy rains and snowfalls in California from the fall through December.

However, Dr. Williams said that January created record dry conditions across much of the West, and February has been dry so far. The reservoirs, which were above normal for the time of year a few months ago, are now below normal again and the snowdrift on the mountains is also suffering. Seasonal forecasts also show that the dryness will continue.

Dr. “This year may be wet, but the dice are loading more and more towards this year, and it looks like it’s going to be an abnormally dry year,” Williams said.

Samantha Stevenson, a climate modeler at the University of California, Santa Barbara, who was not involved in the study, said the research shows the same thing as projections—the Southwest, like some other parts of the world, is getting drier.

“Everywhere isn’t getting drier,” he said. “But in the western US that’s for sure. And this is primarily due to the warming of the land surface, with some contribution from precipitation changes.”

““We are entering fundamentally unprecedented times compared to anything we have seen in the last few hundred years,” he added.