After a winter of low rainfall and record-breaking high temperatures, Californians are consigning themselves to the reality that the current drought, which has been affecting the state since late 2011, will continue into 2015. In its seasonal drought outlook for the upcoming spring, released last week, the National Oceanic and Atmospheric Administration (NOAA) projected drought conditions to persist and possibly even worsen over all of California and Nevada, as well as large portions of Arizona, Utah, and Oregon. Shortly after the release of the NOAA report, California governor Jerry Brown proposed emergency legislation to accelerate the allocation of 1 billion dollars of spending to update municipal water systems and provide financial relief for struggling Central Valley farmers, an addition to a 7.5 billion-dollar emergency water measure approved by the California legislature last November.
Perhaps the most significant indicator of the severity of the drought is the dismally low Sierra snowpack. An early March survey performed by the California Department of Water Resources showed that the depth of Sierra Nevada snow was only 19 percent of average for the beginning of March, only slightly higher than the record low of 18 percent recorded in 1991. The vast majority of California’s precipitation falls between the months of November and April, with rain falling on the populated lowlands and snow piling up in the mountains. After the wet season, California is highly dependent on snowmelt from the Sierras for freshwater, and has invested billions of dollars over the past century in the construction of one of the world’s most sophisticated systems of dams and aqueducts to catch and deliver that water to cities and farmland.
California has always been drought-prone, but the severity of this current drought—2013 was the driest year on record for the state, while 2014 was the fourth driest—have led many to wonder whether global warming may be a contributing factor. A NOAA report released last December claims that the current western drought is being driven by “natural oceanic and atmospheric patterns,” rather than by atmospheric warming. The report’s authors stress that 3 and 4-year droughts are not uncommon for the western US, and cite the development of a persistent area of high pressure off the California coast (what some meteorologists have dubbed the “Ridiculously Resilient Ridge”) as one explanation for why rain is being deflected from the region.
Only a week before NOAA released its report, however, the American Geophysical Union (AGU) released an independent study concluding that the current drought is the most severe three-year drought California has experienced in the past 1,200 years. Using historical tree ring data, researchers determined that while these past several years do not constitute the driest three-year period in the state’s history in terms of precipitation, the current dry conditions are being compounded by record-breaking heat (evaporation rates increase with higher temperatures). The authors of the study contend that both their findings and the ones put forth by NOAA are complimentary, only that AGU draws more attention to the role high temperatures play in exacerbating drought. The findings appear especially relevant in light of the fact that, according to NOAA, the winter of 2014-2015 was California’s warmest since record keeping began in 1895 (the winter of 2013-2014 stands as the second warmest).
While findings may differ as to what role climate change played in beginning California’s current dry spell, climatologists almost unanimously warn that as atmospheric temperatures rise, droughts will worsen over the western United States in the coming decades—largely due to increased evaporation. The situation will be especially crippling in California, with its high population and large agricultural sector. Warmer winters also mean less snow in the Sierras to provide meltwater in the dry spring and summer months. An impending future of perennial drought has led numerous California officials to call for a complete overhaul of the state’s water delivery system, which is still defined by a patchwork of allotted water rights drawn up in the 19th century. While evidence that California lawmakers and citizens are moving towards embracing a complete overhaul is small, a recent poll of likely California voters conducted by the Field Research Corporation found that 94 percent of respondents view the drought as being serious, with a further 68 percent viewing it as being extremely serious. Field Research, which has been polling Californians on public issues since the 1960s, noted that it rarely receives such unanimous responses.