By Stephen Maples
Many are wondering whether the current drought is the harbinger of a drier California with more frequent and longer multi-year dry spells.
Some have already jumped to this conclusion.
“This is the new normal,” Gov. Jerry Brown declared during an April 1 press conference announcing mandatory urban water restrictions statewide, the first in state history. The news media amplified the pithy quote and several other elected officials have repeated the claim as their own.
Brown made the announcement at a snowless Sierra snow survey site. The water content of the mountain snowpack, so crucial to California’s water supply, was only 5 percent of the April 1 average, by far the lowest reading on record for that date.
The governor’s phrase surfaced the following week during a conference on water scarcity organized by UC Davis graduate students. The students asked more than a dozen the speakers, “Is increased water scarcity in the West the ‘new normal’?”
The responses were diverse, suggesting a lack of consensus among water experts. Several speakers answered unequivocally in the affirmative.
“At the end of the day the answer is yes,” said Pat Mulroy, a senior fellow with the Brookings Institution and former general manager of the Southern Nevada Water Authority. “But I think what you’re (also) going to have is much more erratic precipitations. You’re going to have more rainfall, less snowfall. That change alone will make a huge difference and can contribute to the scarcity picture.”
Other speakers – experts in atmospheric science, climatology, history, hydrology and water policy – hesitated to characterize increased water scarcity as a “new normal” without adding qualifiers to their response.
“Climate-wise, the norm depends on what time period you’re looking at…10-year, 30-year, 100-year or a 500-year [or a] 5000-year [period]?” said David Easterling, chief of the Global Applications Division at the National Climatic Data Center.
Paleoclimate records show California has endured “mega-droughts” that lasted more than 100 years. Increased water scarcity, Easterling said, is “probably not” a new norm given the “huge swings” in the Earth’s climate over the eons.
Several studies report conflicting findings on the link between the California drought and climate change. But there is scientific consensus that increasing temperatures under climate change can worsen effects of drought, increasing evaporation and transpiration of surface water and soil moisture.
A warmer atmosphere will take more water from the land, said Reed Maxwell, a hydrology professor at the Colorado School of Mines. “That means the amount of water going into the terrestrial system, going into streams, going into groundwater, going to lakes… it has to be less.”
Other speakers pointed out that water scarcity is driven by both supply and demand.
While it remains to be seen how climate change will affect California’s water supply, water demand is certain to increase, said Richard Howitt, a UC Davis professor emeritus of agricultural and resource economics.
“With or without climate change, environmental requirements, our agricultural crop impacts and our population growth all contribute to increasing scarcity,” Howitt said. “We can cope with it, but we have to be smart about it.”
If anything clear emerged from the “new normal” discussion, it’s that the catch-phrase raises more questions than it answers. The interplay between climate change and water supply at local and regional scales is still poorly understood.
Proclaiming the current drought as the “new normal” under climate change is premature, if not deceptive. But it may help sell Californians on water conservation and prepare them for future droughts, which is likely what the governor and other politicians have in mind.
Stephen Maples, a graduate student in hydrology, helped organize the Water Scarcity in the West conference as a 2014-2015 fellow with the Climate Change, Water and Society IGERT (Integrative Graduate Education Research and Traineeship) program at UC Davis. IGERT Fellows Alejo Kraus-Polk and Lauren Foster contributed to this blog.
Climate Change, Society and Water IGERT, UC Davis
Cook E. et al. 2007. North American Drought: Reconstructions, Causes and Consequences. Earth-Sci. Rev. 81 (1) 93–134
Lund J. 2014. “Could California weather a mega-drought?” California WaterBlog. June 29, 2014.
Swain D. et al. 2014. The Extraordinary California Drought of 2013/2014: Character, Context and the Role of Climate Change [in “Explaining Extremes of 2013 from a Climate Perspective”]. Bull. Amer. Meteor. Soc., 95 (9), S3–S7
Wang H. and Schubert S. 2014. Causes of the Extreme Dry Conditions Over California During Early 2013 [in “Explaining Extremes of 2013 from a Climate Perspective”]. Bull. Amer. Meteor. Soc., 95 (9), S7–S11. PowerPoint version
Funk C. et al. 2014. Examining the Contribution of the Observed Global Warming Trend to the California Droughts of 2012/13 and 2013/14 [in “Explaining Extremes of 2013 from a Climate Perspective”]. Bull. Amer. Meteor. Soc., 95 (9), S11–S15
“But there is scientific consensus that increasing temperatures under climate change can worsen effects of drought, increasing evaporation and transpiration of surface water and soil moisture.”
I disagree. Warmer periods in earth history have been wetter and more zonal and colder periods drier and more meridianal. Not to mention generally more wanky. Consider the d18O from ocean sediment cores:
Perhaps I should add that d18O is our best proxy for temperature, although it also contains a salinity signal.
While I would be cautious to extrapolate the current drought into a “new normal,” I think Mr. Mulroy has it right: as the seas warm and the polar ice shrinks, logically California’s snowpack will decline. Wet years will come back to California but it’ll be more rain and less snow. I can’t imagine a scenario where warming seas and warming air doesn’t result in rising snow levels.
Wouldn’t be the first time? … https://www.hcn.org/issues/44.22/underwater-forest-reveals-the-story-of-a-historic-megadrought
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