A group of researchers at UC Merced has found that climate change means it takes about three months longer for California to recover from drought, and probably longer.
“Climate change has fundamentally changed the odds of getting out of drought. It has weighted the dice,” said Emily Williams, a postdoctoral scholar with the Sierra Nevada Research Institute. “This is happening because of warming in summer months, and a good portion of it is because of human-caused climate change.”
As Californians know, water is a precious resource and needs to be carefully managed to make sure there is enough to meet all needs, from those of the agriculture industry to everyday water users.
Williams worked with engineering Professor John Abatzoglou, SNRI project scientist Katherine C. Hegewisch and UCLA 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.
Drought is a great concern for Californians, and until late 2022, the state had been in a drought for many years.
“The question that was on a lot of people's minds and also in the news was some variation of ‘When is this going to end?’” Williams said. “And because I research climate change, I wondered whether it is getting harder to get out of drought, and if so, how much of it is caused by climate change.”
Decision makers have a lot of tools at their disposal, but the team was concerned they could be inadequate if they only use 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. When all the lines of evidence provided the same answers, the researchers knew they could be confident in their results, detailed in a new paper in the journal Nature Communications: Earth and Environment.
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 from climate change have reduced springtime snowpack because of the shift in rain versus snow and early melt, which leads to less water available in warmer months, the researchers wrote, leading them to conclude their analysis offers conservative estimates of drought recovery time.
