By Jeffrey Mount, Dan Cayan.
During times of extreme water scarcity it is hard to find the silver lining. Yet the severity of this drought, including its record warm temperatures, is benefiting us in one way: it is a window into what droughts may look like in the future and gives us something to plan for—a target, if you will.
The state’s system of water rights laws and water supply infrastructure is built around managing periodic droughts. The design of this system reflects the climate conditions of the late 19th and early 20th centuries, as well as a much smaller population than we have today. Climate models and current observations indicate that we are facing an increasingly different future, one where warm droughts like our current one are no longer the rare exception.
It is crucial that we study our dry years closely. Like past cases, this drought has seen strong rainfall deficits. For four consecutive years (so far), the state has been dry to critically dry, with the driest calendar year on record in 2013. But recent studies have shown that while it has been unusually dry, the precipitation numbers of this drought fall within the realm of natural variability.
What is most unusual about this drought is its exceptional warmth. Statewide, three of the past four winters have been substantially warmer than the long-term average. The past two winters set records that were 4-5 degrees F above average. With this exceptional warmth, California experienced record low snowpack, since much precipitation fell as rain rather than snow and the lean snowpack melted rapidly.
The causes of this drought are being studied and debated by climatologists and oceanographers. Emerging research suggests that this drought may be linked, partially, to very warm waters in the far western tropical Pacific. Heat and moisture pumped into the atmosphere from these waters influence winds and storm tracks in the North Pacific, altering climate patterns in our region.
These teleconnections appear to have created the Ridiculously Resilient Ridge, an anomalous high pressure feature that camped over the waters off the West Coast and pushed North Pacific storms far to the north. This ridge, with its associated weak winds and unusual weather across the eastern Pacific, created The Blob: an area of very warm water stretching from the Bering Sea to Baja California.This blob has disrupted our marine ecosystems, harming fish, sea birds and marine mammals.
Onshore from all of this activity, winter storms that made it off the Pacific Ocean and into California were much fewer than normal. And those that did make it tended to be warm, reflecting conditions in the eastern Pacific, leaving us with rain instead of snow.
To date, there has been no definitive link that implicates this drought as a symptom of climate change. However, the consecutive years of dryness coupled with high temperatures strongly resemble the kind of droughts that are projected under the warmer climate during the latter half of this century. While the origins of future droughts may not be precisely the same, the on-the-ground results are likely to be.
Difficult as it is to endure, this drought provides important lessons. It is a useful and instructive test of how we manage water now—and how we will be forced to manage water in the future. As it unfolds, it tests the resiliency of California’s water infrastructure—made up of dams, aqueducts, and groundwater basins—along with our management systems and institutions. The drought is providing a preview of the warmer conditions during dry spells that will inevitably occur in future decades. As such, it isunveiling future challenges in managing the environment, including conserving our declining native biodiversity.
In short, this drought has revealed what a warmer climate future looks like. We should learn from it and plan accordingly.