New Study Finds Drought Recovery Hindered by a Changing Climate
This news story was based on an article originally published by the University of California Merced.
Drought recovery isn't only important for human water users. For example, migrating birds depend on being able to locate the same sources of water year after year to survive on their long journeys.
A new study, published in Nature Communications: Earth & Environment, found climate change means it takes about three months longer for California to recover from drought, and possibly longer. A group of researchers at the University of California Merced (UC Merced) led this study, with funding from NOAA’s National Integrated Drought Information System (NIDIS) and the National Institute of Food and Agriculture.
“Climate change has fundamentally changed the odds of getting out of drought. It has weighted the dice,” said Emily Williams, the study’s lead author and a postdoctoral scholar with UC Merced’s Sierra Nevada Research Institute (SNRI). “This is happening because of warming in summer months, and a good portion of it is because of human-caused climate change.”
Water is a precious resource and should be carefully managed to make sure there is enough to meet all needs, from those of the agriculture industry to everyday water users. During drought, resource managers want to know when the drought will end to make informed management decisions.
Williams worked with engineering professor John Abatzoglou, SNRI project scientist Katherine C. Hegewisch, and University of California Los Angeles geography professor Park Williams to estimate the odds of recovery in the recent past and historical record, and compare those to what recovery would have looked like in a world without climate change.
Decision-makers have many tools at their disposal, but the team was concerned they could be inadequate if they only used historical data, as there is nothing in the historical record that is analogous to today.
“It was a tricky problem to work on because we were working with probabilities,” Williams explained. “With statistics, you have to have a large sample size, which is fine because these tools had been looking at the past 100 years. But we wanted to look at what happened in the previous 10 to 20 years as compared to the past 100 years.”
They added experimental data and climate model output to solve the problem of small sample sizes rather than looking at just observational data.
The researchers found the probability of drought recovery is about 25%–50% lower in recent decades (2000–2021) than in the historical record (1901–1980), with at least one-third of the reduced recovery probability attributable to anthropogenic climate change. Climate model ensembles show reduced recovery probabilities in the contemporary era (2000–2040), primarily due to increased evaporative demand in non-winter months, resulting in an additional 1–4 months for droughts to recover compared with the historical record.
The researchers caution that the new model does not include some other factors in drought recovery, including changes in the snowpack in California.
Studies have demonstrated that increased temperatures due to climate change have reduced springtime snowpack, because more winter precipitation is falling as rain than snow and what snow does accumulate melts out earlier. This reduces the amount of water available in warmer months, the researchers wrote. Because of these changes, they concluded their analysis offers conservative estimates of drought recovery time.
These findings suggest climate change is slowing drought recovery, with ramifications for water management decisions and drought planning.
Read the full study in Nature Communications: Earth & Environment.
Or, learn more about this NIDIS-funded research project, Improving Drought Indicators to Support Drought Impact Mitigation for Natural Resource Management. Other results of this research include two studies on drought impacts on California national park visitation.
