The drought in California is big news these days, prompting the N.Y. Times to run an in-depth series on “The Parched West” and far-reaching effects of California’s lack of water. Also in the news was a March 12, 2015 OP Ed in the L.A. Times, in which Jay Famiglietti of NASA contends that California “…has only about one year of water supply left in its reservoirs, and our strategic backup supply, groundwater, is rapidly disappearing.”, conjuring visions of Californians laying next to their empty swimming pool, desperately sucking on their garden hose to get one last drop of moisture. Although there are lots of such apocalyptic news stories, it is not likely that California will dry up and become another lost civilization any time soon. But, it is under serious economic, social and environmental stress from the drought. So, serious that the Governor of California, Jerry Brown, recently instituted mandatory water cuts of up to 36% for some water profligate communities and is now calling for fines of $10,000 for water use violations. Governor Brown has said that the drought is not likely to end soon, and that this is the “new normal” for California. But why should people not living in California care about California’s water woes? Surely Coloradans, Utahans, Washingtonians, New Yorkers, and the Chinese, have no stake in the water wars of California. Why not let California dry up, watch those determined desert sands fill up the emptied swimming pools, and we all can get on with our lives without the constant whining from Californians about “their” drought? (For example, see S. Johnson’s pointless essay, “Apocalyptic Schadenfreude”).
Well, there are plenty of reasons, because unlike Las Vegas, what happens in California does not stay in California. California’s tentacles extend far across the globe, reaching into economic, social and environmental realms. Non-Californians should care, because in some way, small or large, how California responds to this present drought will play out across time and space in our highly interconnected and complex world. To understand those interconnections and why California is so important, we would need to dig deep beneath the surface of the headlines and taglines. But, most importantly, at least for this post, is that “The California Drought” is only an extreme indicator of a much broader problem, “The Not-Just-California Drought” with much bigger implications for future water use in the United States.
Although the news media has concentrated on California, the recent drought covers much of the western United States (Figure 1). Overall, it has directly affected over 64 million people. The drought is also long lasting, especially in California, where a persistent dryness has lasted for over 15 years (Figure 2). (Note: Check out this website on the hydrologic effects of the California drought at http://cida.usgs.gov/ca_drought/.)
The perception by water managers is that this drought will not end soon. In a 2013 survey, forty state water managers said they expect water shortages in their states over the next 10 years, even if conditions return to “normal” (GOA 2013). With less precipitation and continued population growth and more water demand, managers expect the situation to worsen, not improve. There are several indicators that drought could be a common feature in the western U.S., not just a short interlude. The first is the record of droughts captured in tree rings; the second is future projections from climate models.
Tree Ring Circus
As trees grow they record the presence of drought years in their yearly growth rings. During wet years trees grow well, producing thick rings; during dry years, when growth is stunted, rings are thin (there are complications that we will not worry about now). Many tree-ring studies over the past have shown that prehistoric droughts of many decades are a common feature of the climate (Figure 3), including two “megadroughts” that lasted for over a 200 years each. The most recent tree-ring research applicable to the California drought was published at the end of last year (Griffin and Anchukaitis, 2014).
These researchers found that, “The current California drought is exceptionally severe in the context of at least the last millennium and is driven by reduced though not unprecedented precipitation and record high temperatures.” But, and this is important, they also found that droughts about as severe as the present one were very common in the tree-ring record. Over the last 1200 years, 37 severe droughts lasted for at least 3 years. Even scarier, they found over sixty periods substantially drier than average that lasted for 3 to 9 years. They conclude that, “the climate system is capable of natural precipitation deficits [i.e., droughts] of even greater duration and severity than has so far been witnessed during the comparatively brief 2012–2014 drought episode.” Based on this prehistoric record of past climate, it is likely that we are in for more and longer droughts and maybe even a megadrought. Not a comforting thought.
Even less comforting—although not as certain—are climate model predictions of future climate. There have been many previous analyses of California’s future climate using global climate models. These are huge packets of computer code designed to simulate Earth’s present climate. Their forbearers are the weather models that meteorologists use to predict the weather. The difference is that the major controls on Earth’s climate, like greenhouse gas effects, can be modified in global climate models to “look” into the future. In the last decade global climate models have been “downscaled” to cover smaller regions, to predict future climates for say, the southwestern United States. These models, in general, predict a future climate for California, that is hotter and possibly even more varied—larger droughts and floods.
In 2014, four researchers (Ault et al. 2014) found that in the southwest U.S., decade long droughts may be much more common in the future under the highest warming scenario. This year, researchers used a large database of drought index combined with downscaled climate model output to calculate the potential for future drought (Cook et al. 2015). They found that droughts in the southwestern U.S. will likely exceed the driest episodes in the last 1000 years (Figure 4). If these simulations are correct, over the next 85 years California and the surrounding southwest U.S. region may inexorably move into persistent drought conditions.
This is a daunting prospect for the California water system considering how stressed it is under the present drought. Others in the southwest should not be too smug though, for their time is very likely coming, which if you live in Texas is pretty obvious.