Report: Heat and Climate Change Help Fuel California’s Drought

These NASA images from 2013 and 2014 illustrate the impact of the drought.
These NASA images from 2013 and 2014 illustrate the impact of the drought.

Earlier this year, reports showed the several consecutive dry years combined with record supercharged California droughts. In 2014, temperatures were by far the highest – fueled mainly by a warmer than normal winter – in the 120 years of record-keeping. On average it was 1.8 degrees Fahrenheit warmer than the previous standard, set in 1934.

By 2014, even though precipitation was near average, the state got roughly as much usable water as in 1977, one of the lowest years on record, said Michael Dettinger of the U.S. Geological Survey.

The problem was that the combination of heat and lack of precipitation created the worst drought conditions in the state in 1200 years. While precipitation was low, it was not unprecedented. It was the heat that pushed the drought to the next level.

Now the LA Times is reporting that climate change is likely to increase the risk of severe drought by overlapping warm and dry periods with increased frequency.

“The key for drought stress is not just how much precipitation there is,” said Noah Diffenbaugh, the lead author of a critical new study and an associate professor at Stanford University’s School of Earth, Energy and Environmental Sciences. “Temperature is an important influence on the water available in California.”

The impact of temperatures leads to increased evaporation and a reduction in the amount of moisture in the soil – the leads to an intensification of California’s dry season.

When they analyzed historical climate data, “they found that warm-dry years have occurred more than twice as often in the last two decades than they did in the preceding century.”

Worse yet, “It appears that the situation is set to get worse. A continuing rise in global temperatures — fueled in part by human activity — will greatly increase the chances that dry periods are accompanied by warm conditions, the team predicted. That’s what has happened during the state’s current drought, now entering its fourth year and by some measures the worst on record. “

“Our results highlight the fact that efforts to understand drought without examining the role of temperature miss a critical contributor to drought risk,” wrote the authors, whose work was published Monday in the Proceedings of the National Academy of Sciences.

At the same time, the question of climate change on overall impact on the California drought is a subject of debate. A published report from last year “concluded that there is no definitive link.”

However, a paper published by Noah Diffenbaugh and Stanford graduate student Daniel Swain, a co-author of the PNAS (Proceedings of the National Academy of Sciences) study, “contributed a paper that said the type of stubborn high-pressure system that persistently pushed storms north of  the state is more likely to occur with climate change, suggesting a link to global warming.”

Others disagreed and attributed the drought to natural variability. They write that there was “no appreciable long-term change in the risk for dry climate extremes over California since the late 19th century.”

But the question is not merely one of lack of precipitation, but of the combined effects.

“In the PNAS study, Diffenbaugh, Swain and Stanford graduate student Danielle Touma note that California’s average precipitation has not appreciably declined over the last century. Indeed, climate models suggest that winter precipitation in much of the state could modestly increase this century,” the Times writes. Rather, it is rising temperatures that contribute to the increasing drought risk.

“There’s no question that low precipitation is a prerequisite for severe drought in California but it’s not sufficient,” said Mr. Diffenbaugh. “The efficiency of low precipitation turning into severe drought is much higher if there are warm conditions.”

Prior to 1995, nearly half of the moderately dry years overlapped with warmer temperatures, but since then, every dry year has coincided with a warm year. That’s because, overall, 80 percent of the years since 1995 have been warmer than what was normal for California.

“It used to be flipping two coins independently and getting two tails one-quarter of time. Now we’re getting tails on the temperature coin much more often,” Mr. Diffenbaugh said.

“The emergence of a condition in which there is ~100% probability of an extremely warm year substantially increases the risk of prolonged drought conditions in the region,” they concluded.  “Our results strongly suggest that global warming is already increasing the probability of conditions that have historically created high-impact drought in California.”

The problem is that their models suggest that, by 2030, the temperatures that drive this drought condition could become a yearly occurrence.

“We’re not arguing every year will be a drought year. But even without any change in precipitation, when low precipitation years occur, there’s 100 percent risk they’ll be occurring in warm or even extremely warm conditions,” Mr. Diffenbaugh said.

—David M. Greenwald reporting

About The Author

David Greenwald is the founder, editor, and executive director of the Davis Vanguard. He founded the Vanguard in 2006. David Greenwald moved to Davis in 1996 to attend Graduate School at UC Davis in Political Science. He lives in South Davis with his wife Cecilia Escamilla Greenwald and three children.

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  1. LadyNewkBahm

    “The record-breaking cold we saw in February will continue into the first week of March for a number of cities in the Midwest, South and Northeast. ”

    “Dozens of record lows will be threatened late this week, and some cities could see their coldest temperatures in decades for so late in the season.”

    Lows: Subzero lows from northern Illinois and northern Iowa to the Canadian border. Teens and 20s in the Mid-South and southern Plains. A handful of daily record lows will be threatened in the Midwest and southen Plains.
    Potential Daily Record Lows (record to beat is in parentheses): Chicago (0 degrees) | Dubuque, Iowa (minus 9 degrees) | Dallas-Fort Worth (20 degrees)
    Latest Subzero High Since 1982? If Chicago falls below zero, it would be the latest in the season a subzero low has occurred there since 1982. Also, it would only be the fifth time since 1872 that a subzero low has been recorded on March 5 or later.
    Highs: Teens and 20s for highs in the Great Lakes and interior Northeast. 30s and 40s push into parts of the South.

    San Francisco, Seattle, Salt Lake City and Las Vegas were among cities blessed with record-balmy winters. But a couple thousand miles away, February brought a snow record for Boston’s and record cold for Cleveland, Buffalo, Syracuse, N.Y.; Harrisburg, Pa., and several other cities. Chicago tied its February cold record.

    “That sharp contrast isn’t surprising,” AccuWeather senior meteorologist Tom Kines told USA TODAY. “That’s how the atmosphere and Mother Nature work.”

      1. Barack Palin

        When the conditions don’t fit the climate alarmist’s agenda they’ll say it’s just “weather” not “climate”.

        How many drought cycles have we had in California over the last century?  10?  12?  15?

        It’s just another cycle but I fully expected the alarmists would try and make hay over it.

        1. Frankly

          Right.  And when California floods again, the alarmists will again blame global warming.

          Global warming is not so much a scientific theory any longer as it is a mechanism to help secular people fill their God-gap, and also a mechanism of the left to wage war on capitalism and industrialism.  The science aspect of it is de minimis now.

          1. Don Shor

            a mechanism to help secular people fill their God-gap,

            This kind of commentary is not useful.

            The science aspect of it is de minimis now.

            Climate change is a very robust field in geophysics. The science aspect is certainly not “de minimis.”

        2. TrueBlueDevil

          When I learned that the oceans released 330 gigatonnes of CO2 every year, that made me pause at the enormity of nature.

          Then the fudged data, repeatedly.

          One urgent solution is to build / expand more reservoirs, and to limit immigration … as people require water. I mean, if they’re really serious …

        3. TrueBlueDevil

          But it certainly seems like there are a lot of people masquerading as “experts” who aren’t, who have agendas, who lie, who manipulate, who are getting a lot of funding from the Warming crowd, and therefore cast a shadow on much of what they say.

          Some of these people were pushing global cooling a few decades back.

          They win either way, hence the political gamesmanship of going from “global warming” to “climate change”.

          1. Don Shor

            There are tens of thousands of geophysicists working in the field of climate science. How many of them are you familiar with?

        4. hpierce

          ‘Climate change’ is real.  A lot of natural processes go into that.  The earth has experienced climate change since it was new, and most of that time there were no humans.  It has been like a pendulum.

          The questions are, 1) is it currently affected by human behavior? 2) is it deleterious, or in the ‘big scheme’, beneficial (and to who/what)? 3) can we change the changes? 4) should we?

        5. wdf1

          Frankly:  Global warming is not so much a scientific theory any longer as it is a mechanism to help secular people fill their God-gap, and also a mechanism of the left to wage war on capitalism and industrialism. 

          More partisan trolling.

          1. Don Shor

            One degree Celsius increase would have beneficial impacts in some areas, and harmful impacts in others. Since it would be gradual, we would be able to adapt to it if we plan for that. Less-developed countries would have greater difficulty planning and adapting. The Netherlands can deal with any sea level rise over several decades. Bangladesh might have more difficulty doing that.

        6. Davis Progressive

          “CO2 is plant food, right?”

          sure and if you plant a bunch of trees, you might be able to reduce co2 in the atmosphere somewhat, which is why cutting down a tree and burning it is so bad, you end up removing a co2 reducer and release its co2 back into the atmosphere.   deforestation is a problem.  however, we have to deal with fossil fuels to really start getting at the problem.  it may frankly be too late.

        7. TrueBlueDevil

          DP, I think you need to talk to China and India, we’ve cut our CO2 by 20 percent thanks to natural gas (NG), fracking, and converting coal plants to use of NG. Build more nuclear plants, insulate.

          What is your stance on salvage logging in areas that have ad huge fires, or huge beetle infestations?

          Take the Rim Fire, which burned over 250,000 acres. We will salvage less than 10 percent of the usable trees / wood. The way I see it, salvage a lot more, use the funds to help replant trees, and Americans would benefit from cheaper wood prices. Win-win-win. Same for the trees killed by beattles, which are ravaging some areas unchecked.

        8. wdf1

          TBD:  …hence the political gamesmanship of going from “global warming” to “climate change”.

          The first time I remembered hearing of phrase “climate change” in a big way was Frank Luntz,  ca 2002.  He was recommending that political conservatives use climate change rather than global warming.

      2. Davis Progressive

        all your comment demonstrates is your fundamental lack of understand for what “climate” change means and how it will manifest itself.  a weather occurrence neither proves nor disproves climate change.  in this case, the research suggests that climate change may increase the frequency of the confluence between heat and low precipitation to increase the frequency and severity of drought.

        that doesn’t mean there won’t be times when locally it won’t be cold.  the interesting thing is despite the cold snap in the east (which is a biproduct of our own lack of rainfall and the blocking high) is not sufficient to offeset the overall warm winter globally.


        1. Frankly

          Maybe the drought is God’s way to punish California for the sinning ways of its people.  That theory has about as much credibility as does the claim that the drought is a byproduct of man made Co2.

          1. Don Shor

            Increased global temperatures would increase the severity of drought and the severity of flooding.
            With respect to drought, Dr. Roger Pielke Sr., who is often at odds with climate alarmists, is noted for his work on regional impacts of climate change. Here is one example:
            You might find his research interesting.
            Not to be confused with his son Roger Pielke Jr, who is also often at odds with climate alarmists ( Pielke Jr focuses on the economic and political impact of climate change and natural disasters.

        2. dlemongello

          Thanks for writing my comment for me DP.  What I’ll add is no matter what the cause, the reality is we need to start using water in a new way or we risk an incredible crisis.  I have made this a personal challenge, almost a game, how little can I use.  It is kind of fun, ask Matt, he has seen what I do (if he was paying attention :)).  Oh yes, I still “allow” my husband to take “real” showers, but we save and use all the water. Some say the wheel was the greatest invention, the bucket is not far behind.

        3. hpierce

          Frankly, the shorter term changes may have to do with our reductions in SO2… sulfur dioxide emissions have been drastically reduced, part of efforts to reduce ‘acid rain’, which was a good thing.

        4. TrueBlueDevil

          dlemongello, you’re on to something. We could copy the French and bath once a week, and copy their slow economy, which results in less need for other resources.

          But the [edit: French] do have it right on power, they have the cleanest air in Europe with nuclear power (no CO2 or horrible emissions due to burning coal), cheap energy, and make money selling excess power to neighboring countries.

          [moderator] edited for language.

  2. David Greenwald

    Links automatically put a post into the moderation status as an anti-spam feature. One of the people with administrative authorities will typically hit approve once they see it’s a legitimate post.

    1. Matt Williams

      To clarify, one link in a comment does not put the comment into moderation “pending” approval; however, more than one link in a comment does trigger the “pending” feature. wdf1 frequently posts comments with more than one link, and he/she can attest to the fact that they are removed from “pending” status quickly and consistently.

      With that said, there were two posts made over the weekend whose links (and content) was so off-topic that their next destination after “pending” status was “off-topic deletion.”

  3. TrueBlueDevil

    We built the 8th largest economy of the world in a Mediterranean climate, and now we’re surprised that we have water issues?

    If the those who believe in Global Warming are serious, here are some real solutions, in California:

    1. Stop growing cotton in the Central Valley, a water intense crop (they may have already done this)

    2. Build more reservoirs, a large one south of the Sacramento River – which has larger water flows than the Colorado River – seems logical.

    3. Expand Shasta Dam; it was designed for a larger size.

    4. Limit immigration, and close the border. People use water. I believe even the Sierra Club had a fight over this a few years ago. You can’t grow from 15 million to 35 million and not expect your infrastructure (like dams) to not grow. And we’re probably on our way to 60 or 70 million.

    5. I’ve heard a few people theorize that the huge forests we now have, and lack of thinning, that the thick forests may also be retaining some water.

    6. Re-certify the nuclear power plant in San Diego: NP emits zero CO2.

    7. Stop the plan to build the California High Speed Rail (HSR), an extremely energy intensive heavy-rail project that will add huge amounts of CO2 to the environment.

    8. Explore building desalination plants (cost / benefit).

    9. Crazy idea? Explore the feasibility and cost of funneling water into California from Southern Oregon.

  4. Anon

    What bothers me is how much the “climate change theory” has been politicized on both sides of the aisle.  For me, the real issue is air pollution, something that would be good to reasonably minimize.  China is a perfect example of what can happen if a country refuses to worry about air pollution – smog so bad there are days when it looks almost like night.  However, there is also the law of diminishing returns.  Are we spending enormous amounts of money to achieve de minimus decreases in air pollution?

    Secondly, it must be remembered that only 10% of CA’s water is urban use.  The rest is used by farmers and environmentalists.  Even if urban use was cut in half, which would be an extremely drastic reduction, the most that could be achieved by cities in water savings is a measly 5%.  It is time for the gov’t to take a look at how much water is being slurped by farmers and environmentalists – something that will take place soon under new CA legislation regulating the use of ground water.

    1. Davis Progressive

      “What bothers me is how much the “climate change theory” has been politicized on both sides of the aisle.”

      i don’t see how you can avoid that.  first, if one side is completely denying the problem – how do you work to create solutions when one side refuses to acknowledge the problem.  under normal conditions i tend to agree that alarmists are not the ones who are usually correct.  but unfortunately, the consequences for warming could be catastrophic.  worst case scenarios do happen at times.

      ” For me, the real issue is air pollution, something that would be good to reasonably minimize.”

      i won’t minimize the problem of air pollution, and certainly the emissions of greenhouse gas are part of that, but the problem of air pollution pales to the global impact of temperature increase over time.

      1. Anon

        If GHG emissions are part of the air pollution problem, then how does the “air pollution problem pale to the global impact of temperature increase over time”?  Framing the issue as air pollution instead of global warming would be far more effective in getting the job done because it is much more difficult to argue against “clean air” than the more convoluted/complex global warming theory!  Sheeeeeeeeesh!

    2. TrueBlueDevil

      Most of the water that flows down the massive Sacramento River just rushes out to the Pacific Ocean. We should store more of that valuable resource, and new reservoirs are also used for recreation and wildlife.


        1. Don Shor

          Sites réservoir is practically a no-brainer. The state should move faster on that. San Luis reservoir could be expanded, and environmental groups aren’t even opposing that.

    3. Frankly

      You can thank Democrats – specifically Al Gore for getting it started as a political rather than scientific debate.  It is now part of the war on capitalism and the war on industrialism.  It primarily supports a hard-left extreme environmentalism worldview.

      There is plenty of evidence that the theories and impacts are over-hyped.  There is plenty of evidence and agreement that there is little we can do to slow the rate of man-made influence to climate change.

      Instead of honestly analyzing why there is a large percentage of people in the US and world that believe the theories of man-made climate change are political and ideological rather than based on proven and provable science, those on the left only label those that disagree or disbelieve as ignorant.  And the response to that is growing opposition.  This happens for two reasons:

      One – there is plenty of data and science out there shooting holes into the existing theories… primarily that the climate models have drastically failed to predict the actual climate over the last 15-20 years.   When thinking people read that information and then get to hear the climate alarmists labeling those that disagree or disbelieve as ignorant, they start to recognize that politics has taken over the science.

      Two – because even scientists agree that there is nothing we can do to stop man-made climate change (if it even exists) the lack of demand for adaption and the continued demand for more and more reductions in consumption makes clear that politics has taken over the science.

      1. Dave Hart

        Maybe the question is save capitalism and ditch the planet or ditch capitalism and save the planet.  The question will come into focus as the intensity of climate changes force the question out into the open, i.e. when it objectively restricts our freedom to continue as we have in the past.  After spending 30 years as a snowpack hydrologist and steward of the 100+ year database on Sierra snow water content, I can tell you I am a believer that comparatively sudden changes are in motion even though I don’t pretend to claim the expertise to prove anything one way or the other.

        You seem to worry about the issue being politicized.  The policy that you or I adopt as individuals is no less politics than that worked out by governments.  It’s a matter of scale.  Politicizing any issue is not inherently a bad thing.  All it means is that people are finding the issue important enough to develop a policy to address the effects of whatever the issue is.  That’s politics and so be it.  What else would you have people do?

        One thing for sure is that the degree to which climate change is real and significant, the policies will be developed and implemented on a wide scale and by mass organizations and government.  You are just as free to join the Koch Brothers’ well-funded political attempts to downplay human caused climate change as the rest of us are to join  It’s politics after all.

  5. dlemongello

    I include agriculture  in my general statement that we have to change how we use water.  However 1)  no matter the percentage, every gallon we waste for any reason is a gallon we may need later the worse the drought gets, 2) Growing food is more important than frivolous urban uses and 3) Agricultural waste of course doesn’t cut it either.

    1. Anon

      Excuse me?  “Frivolous urban uses”?  Let’s see how long you would last without drinking water!  And are you proposing to allow all the vegetation in Davis to die?  No wildlife sanctuaries?

        1. Tia Will


          Your defense of the status quo and our consumption based economy seems to fly directly in the face of your frequently stated claims that the “baby boomers” have been a self centered and greedy lot. I agree that we have, as a society, become very self centered, materialistic and greedy and that we are likely to be giving our children and grand children a much less sustainable environment because of our consistent adherence to a “my material well being above all else” point of view.

          I agree with dlemongello that many of our urban uses of water are indeed frivolous. Kind of reminds me of the gardens maintained by the high priestess in Dune while water markers were a treasure to be traded and given as precious gifts by the general populace while she basked in her greenhouses with her fountains and orchids.

  6. tribeUSA

    A couple of California hydro observations not mentioned in the article posted, from a study based on Sierra Nevada precip & streamflow since the 1920s:

    (1) A distinct trend of increasing inter-annual variability in both precipitation and streamflow. Although there have been no statistically significant trends in mean annual precipitation or mean annual streamflow (Sac & San Joaquin & major Sierra tributaries) since circa 1920 (possibly earlier); there has been a huge increase in inter-annual variability. So dryer drought years and wetter flood years. Will the trend continue?

    (2) At least two independent studies (that I know of) document a trend of decreasing response of streamflow to precipitation in the northern Sierra Nevada. One  hypothesis for this trend is that when more winter precipitation falls as rain rather than snow (due to warming, which has been larger during the winter than the summer); a larger fraction of that rain-precipitation evaporates as compared to the snow-precipitation. (think multiple episodes of wet soil & soil evaporation and plant transpiration for rainfall events; whereas for snowpack the moisture is released as a smaller number (maybe 1-3) of big slugs, and most of it flows into streams before it can evaporate).

  7. Anon


    California’s current drought is being billed as the driest period in the state’s recorded rainfall history. But scientists who study the West’s long-term climate patterns say the state has been parched for much longer stretches before that 163-year historical period began.

    And they worry that the “megadroughts” typical of California’s earlier history could come again.


    Through studies of tree rings, sediment and other natural evidence, researchers have documented multiple droughts in California that lasted 10 or 20 years in a row during the past 1,000 years — compared to the mere three-year duration of the current dry spell. The two most severe megadroughts make the Dust Bowl of the 1930s look tame: a 240-year-long drought that started in 850 and, 50 years after the conclusion of that one, another that stretched at least 180 years.”


    1. Dave Hart

      None of that means much in relation to this issue of climate change to the extent human activity has an impact unless you are arguing that human activity will lessen the length or severity of drought.  I have seen no physics based models that imply that is a probable and consistent result. These tree-ring studies reveal what was happening under a given set of circumstances for atmospheric carbon and other greenhouse gases at the time.  It could just as logically follow that the 240-year drought could now be a 350-year drought.  It doesn’t negate the impacts of putting carbon back into the air from where it remained sequestered for millions of years.  Removing carbon from the ground in the form of coal and petroleum that originated as plant and animal matter and putting it all back into the atmosphere as a gas is a way of running the clock backward millions of years.  We have our own time machine.  Can’t wait to see what fun it will bring!

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