In the summer of 2020, the U.S. Drought Monitor turned 21. This month, six of the USDM authors published an article in Weatherwise chronicling the map’s history and use. Developed by current National Drought Mitigation Center director Mark Svoboda and former National Weather Service Climate Prediction Center meteorologist Douglas Le Comte, the U.S. Drought Monitor combines a collection of drought-related indices, indicators and tools into a single user-friendly map that shows where drought is and isn’t.

The article details how the map has evolved over time, and how it has become a trigger for issuing over $7 billion in federal aid to livestock producers who have endured severe and/or extensive droughts.

In the future, Svoboda says in the article, he expects that improved computing and deep learning tools will lead to continued improvements in detecting and reporting drought across the U.S. and its territories. And the USDM authors write that they hope to bring more citizen scientists into the on-the-ground network.

A new study led by researchers at the University of Cambridge found that recent European summer droughts have been more severe than anything experienced in the continent’s past 2,100 years. 

According to a Cambridge release published in ScienceDaily, the international team of researchers examined “the chemical fingerprints in European oak trees to reconstruct summer climate over 2,110 years.” What they found was a long-term period of drying that suddenly intensified from the summer of 2015 through 2018.

"We're all aware of the cluster of exceptionally hot and dry summers we've had over the past few years, but we needed precise reconstructions of historical conditions to see how these recent extremes compare to previous years," said first author Professor Ulf Büntgen from Cambridge's Department of Geography, who is also affiliated with CzechGlobe Centre in Brno, Czech Republic. "Our results show that what we have experienced over the past five summers is extraordinary for central Europe, in terms of how dry it has been consecutively."

To be in a megadrought, an area as a whole must experience drought for two decades or more. With over 41% of the West experiencing severe or exceptional drought according to the latest U.S. Drought Monitor, national media attention has increased coverage of the topic in recent weeks. As Vox reporter Lili Pike recently wrote, “a greater stretch of the West has been in the most severe category of drought than at any time in the 20 years that the National Drought Mitigation Center has been keeping records.”

Pike spoke to USDM author and NDMC climatologist Brian Fuchs about the causes of the drought, which include a weak Southwest summer monsoon, lacking rain and heat waves.

“If I had to pinpoint one thing that really drove the drought to where we are right now, it was the heat of last summer,” Fuchs said. 

The La Niña weather pattern in part has limited rainfall and snowfall in the West during the winter season, Pike wrote, and many areas have not made up for dryness that intensified during dry months. 

Using radiocarbon dating and optically stimulated luminescence to examine a set of ancient irrigation canals led a team of researchers to propose that central Asian civilizations of the  Otrār oasis weren’t brought down by warfare alone. Drought likely played a major role, Eos writer Richard J. Sima reports.
 
The study, published in the Proceedings of the National Academy of Sciences of the United States of America, examined a region of what is now Southern Kazakhstan where Mongols invaded in the early 13th century.
 
“The region flourished during classical antiquity because of its position on the Silk Road and access to floodwater-irrigated land spanning some 50,000 square kilometers—about twice the size of Mesopotamia,” Sima wrote. “At its height, the region became known as Transoxania and was described as the ‘land of the thousand cities.’”
 
Its decline aligned with the invasion, and the area was completely decimated by the 17th century, Sima wrote, but the researchers were able to determine that canals had fallen into a state of disrepair about a century before the invasion. By reconstructing climate records, the researchers found that the canals were abandoned during prolonged drought periods, Sima wrote.

 “People and communities lived and were shaped by the environment,” Mark Macklin told Eos. Macklin, one of the lead authors of the study, is a distinguished professor of river systems and global change at the University of Lincoln in the United Kingdom. “And in the case of central Asia, [they] may be shaped by the availability of water.… If you don’t have water, you don’t have crops, you can’t live.”