Climate Change Research Spotlight

Global Warming Intensifies Drought Conditions in California

The rise in global temperatures has amplified naturally occurring drought conditions in California and has increased the chance of severe droughts in the future.

Source: Geophysical Research Letters

By

The Golden State earned its name for the precious metal, but for the agricultural giant, the most precious commodity of all might be water. The recent drought dealt a heavy blow to western states, which manifested in groundwater depletion, fields left fallow, tree die-offs, and the latest rise in wildfires. The 2012–2014 drought broke records in California’s key agricultural regions, and conditions in 2014 were record-breaking statewide.

A recent study evaluates the role of anthropogenic climate change on these severe drought conditions. The new insight is fundamental to better protecting communities and ecosystems that depend on California’s most precious resource. Decreasing soil moisture, lowering river levels, and diminishing groundwater reserves could be disastrous for the state, especially in the Central Valley, the primary agricultural region that relies on steady irrigation.

Williams et al. drew data from the Palmer drought severity index, a proxy for drought conditions that calculates near-surface soil moisture from precipitation and temperature records.  They looked at records between 1901 and 2014 to identify the impact of rising global temperatures on drought severity. The team also worked to distinguish natural temperature variability from anthropogenic warming. The authors conclude that “anthropogenic warming is estimated to have accounted for 8–27% of the observed drought anomaly in 2012–2014 and 5–18% in 2014.”

The researchers found that the current droughts naturally occur but got intensified by the rise in global temperatures since 1901. Although lack of precipitation is still the primary driver of drought, anthropogenic warming has resulted in a significant trend toward drought and has increased the probability of severe drought overall.

The trend toward drought emerged because warming disrupts the natural climate variability that would normally offset drying. Warming since the early 1900s causes an additional 9 centimeters of annual evaporation during a given year, effectively making each rain drop or snowflake less valuable to humans and ecosystems because it is more readily evaporated.

With warming projected to continue throughout the 21st century, this study highlights the need for long-term planning to improve drought resilience. A steadily warming planet will have profound local impacts that require conscientious resource management to safeguard lives and livelihoods. (Geophysical Research Letters, doi:10.1002/2015GL064924, 2015)

—Lily Strelich, Freelance Writer

Citation: Strelich, L. (2015), Global warming intensifies drought conditions in California, Eos, 96, doi:10.1029/2015EO034713. Published on 26 August 2015.

© 2015. The authors. CC BY-NC 3.0
  • bob ashworth

    All gases, including CO2, and dust cool our planet. CFC destruction of ozone made the stratosphere cool around 1.4 C and the earth to warm 0.5 C (more UVB light hits earth now). The ozone concentration in the stratosphere should return to normal around 2100.

    • Dano2

      That’s good comedy!

      Best,

      D

      • bob ashworth

        They have been lying about CO2. Don’t think there are many real scientists anymore; or they have become nefarious. I am an old chemical engineer who has analyzed mass and energy balances around systems for years. It was simple to analyze why the earth warmed. With no real science being promoted anymore, I feel sorry for our children.

        • Dano2

          Plot idea: 97% of the world’s scientists contrive an environmental crisis, but are exposed by a plucky band of billionaires & oil companies.

          Best,

          D

          • bob ashworth

            Another lie. I and ~31,500 scientists signed the Oregon petition against the Kyoto Protocol that promoted climate change from CO2. http://www.petitionproject.org/
            Including Dr. Edward Teller who developed the hydrogen bomb! Name one of these your so-called 97%.

            • Dano2

              Oh. My. Goodness. OISM is an instant disqualifier for the credibility race. Civil society does not discuss such things.

              Best,

              D

              • bob ashworth

                Another lie by the AGW crowd. The AGW crowd has no scientists supporting them unless they are getting money from the Obambam administration.

                EPA Administrator Gina McCarthy told Congress that the Agency’s proposed standards for coal fired power plants, is, in fact, an opportunity for economic growth: “The great thing about this proposal is that it really is an investment opportunity. This is not about pollution control.”

                EPA’s heating model (MAGICC) shows the clean coal plan will prevent less than two-hundredths of a degree Celsius (0.018 oC) of global warming by the end of this century. This temperature change is so small it could never be confirmed by man – that is why the EPA hasn’t relayed the effect. They work for the Liar-in Chief!

                • Dano2

                  You have no credibility, due to citing OISM, and piling on obvious in-group identifiers as “AGW crowd’ and ‘Obambam’. You have discredited yourself . Civil society does not discuss such things.

                  Good day.

                  Best,

                  D

                • bob ashworth

                  Civil society controlled, the liberal crowd which you are apparently are apart don’t no how to respond to facts. You couldn’t even name one scientist who believes in global warming; this doesn’t surprise me..

            • Dano2

              One loses all credibility when one cites the OISM.

              Best,

              D

    • Dano2

      All gases, including CO2, and dust cool our planet.

      Yet GHGs warm the planet, as science has shown us for over 150 years. Who should I believe: scientists or random internet commenter guy?

      Best,

      D

      • bob ashworth

        Use common sense then. When you go outside on a sunny day and a cloud goes overhead most people feel cooler, but maybe not you. Water vapor (clouds) is the greatest greenhouse gas claimed by the pseudo-scientists.

        • Dano2

          WV is a (positive) feedback due to its residence time in the atmosphere. But you know that because you claim to be a scientists.

          And since you are a scientists, you know how cold the planet would be if the GHGs were taken out of the atmosphere. You also know that in the late 1800s a Nobel was awarded to the man who calculated how much earth would warm if CO2 doubled. And you know of the recent experiment that measured precisely the amount of radiative forcing from CO2 alone at the earth’s surface.

          You know all these things because you have told us you are a scientists.

          Best,

          D