A new study reports that the U.S. Drought Monitor's weekly maps of nationwide drought conditions -- which help direct emergency federal aid -- have captured the steady march of climate change, but the Drought Monitor has itself failed to adapt to that reality. Areas of the country are spending more and more time in severe drought conditions the Drought Monitor still considers to be rare occurrences.
"The system we use for emergency response to drought conditions is being co-opted by a changing climate," said senior author Justin Mankin, a Dartmouth associate professor of geography and director of the Climate Modeling and Impacts Group. He directed the study in his role as co-lead of the National Oceanic and Atmospheric Administration's Drought Task Force and a NOAA grant supported the research.
Each week, experts compile analyses to determine the severity of drought experienced at national, state, and regional levels based on precipitation, soil conditions, reservoir levels, temperature, and agricultural losses, as well as reports and advocacy from local politicians and stakeholders. The Drought Monitor then publishes a map with severity denoted by color, from white indicating no drought to maroon signifying extreme conditions.
"While these percentile thresholds are static, the climate is not," said Zhiying Li, the paper's first author and an assistant professor at Indiana University who began the study as a postdoctoral research fellow at Dartmouth."The ongoing aridification and worsening droughts in certain regions may change what was once perceived as an anomaly, making it less of an emergency anymore.
The result is that sections of the country have been colored maroon for weeks or months on end, Mankin said."What value to decision-making is a map that is red everywhere all of the time?" he asked.