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California’s drought, and recent trends, may pale beside our probable future

REUTERS/David Becker
Arizona’s Lake Mead’s water levels have dropped precipitously with 11 of the past 14 years marked by deep dry spells.

Minnesota has had its brushes with drought in recent years, but nothing like the experience of the American Southwest, where 11 years out of the last 14 have been marked by seriously deep, dry spells across large parts of Arizona, Nevada, New Mexico, Oklahoma and Texas.

Not to mention California, now in its fourth year of a drought that could go into the record books right now as the worst in more than a thousand  years.

Such a comparison is possible – and verifiable – because of tree-ring data assembled into the North American Drought Atlas, which came out in 2009 and presents a record stretching back roughly 2,000 years.

Two millennia is an unusually long timeframe for climate data, and last week the atlas enabled this striking conclusion from climate scientists at NASA, Columbia and Cornell:

Under any reasonable outlook for global warming over the rest of this century, both the American Southwest and the central Great Plains – including much of Minnesota – are likely to experience drought on a level “unprecedented” since the year 1000, and significantly more severe than a pattern known to have occurred early in the last millennium.

I put the quotes around “unprecedented” not to qualify it, nor to quibble with it, but because it is precisely (and I think remarkably) the term used in the title of the paper, which was unveiled late last week at the American Association for the Advancement of Science’s annual conference in San Francisco, and published simultaneously in AAAS’s new online journal, called Science Advances.

(Because it’s an open-access journal,  you can read Unprecedented 21st century drought risk in the American Southwest and Central Plains for yourself without fee and at your convenience.)

The paper’s point is not that the coming drought regimes lack for serious though less severe  predecessors. In medieval times, the paper says, both the Southwest and the Central Plains  experienced “megadroughts” — periods of seriously depressed soil moisture much worse than anything in the so-called historical period of 1850-2005.

Disappearance of the Anasazi

For one example, there’s the prolonged drought about 1,300 years ago that is thought to have wiped out the Anasazi Indians and the pueblo culture they had developed on the Colorado Plateau, in today’s Four Corners region.

And as shown in the graph below, from an earlier paper on megadroughts as recorded in tree rings, the current patterns are approaching the intensity of some earlier extremes.

But megadroughts of the future, according to the new publication, will be worse, because of global warming and other climate shifts driven by our loading of the atmosphere with greenhouse gases.

From the announcement issued by Columbia:

Many studies have already predicted that the Southwest could dry due to global warming, but this is the first to say that such drying could exceed the worst conditions of the distant past. The impacts today would be devastating, given the region’s much larger population and use of resources.

“We are the first to do this kind of quantitative comparison between the projections and the distant past, and the story is a bit bleak,” said Jason E. Smerdon, a co-author and climate scientist at the Lamont-Doherty Earth Observatory, part of the Earth Institute at Columbia University. “Even when selecting for the worst megadrought-dominated period, the 21st century projections make the megadroughts seem like quaint walks through the Garden of Eden.” 

“The surprising thing to us was really how consistent the response was over these regions, nearly regardless of what model we used or what soil moisture metric we looked at,” said lead author Benjamin I. Cook of the NASA Goddard Institute for Space Studies and the Lamont-Doherty Earth Observatory. “It all showed this really, really significant drying.”

Reaching this conclusion required aligning tree-ring data with three modern metrics of available soil moisture, to “calibrate” them, then aplying the forecasts of 17 state-of-the-art climate models. (Interestingly, Ben Cook’s father, Ed, is also a father of the atlas project.)

Regardless of how soil moisture is measured, its essential drivers are only two – how much precipitation falls on the ground, and how quickly it evaporates back into the atmosphere. Both can be expected to change with continued global warming.

While much of the current conversation about impacts, adaptation and mitigation strategies centers on precipitation – because water is so critical, and because shifting rainfall patterns are difficult both to predict and to manage around — it looks like the latter is going to be the bigger drought driver. From the paper:

All three moisture balance metrics show a remarkably consistent drying during the later half of the 20th century. Drying in the Southwest is more severe than that over the Central Plains. In both regions, the consistent cross-model drying trends are driven primarily by the forced response to increased greenhouse gas concentrations…

Even though cold season precipitation is actually expected to increase over parts of California in our southwest region, the increase in evaporative demand is still sufficient to drive a net relocation in soil moisture.

Over the Central Plains, precipitation responses during the spring and summer seasons (the main seasons of moisture supply) are less consistent across models, and the drying is driven primarily by the increased evaporative demand.  

Two scenarios, both sobering

The researchers also considered two scenarios for global warming over the rest of this century: the RCP 8.5 or  “business-as-usual” scenario, in which emissions continue to increase on pretty much on their present course, and “middle-of-the-road” RCP 4.5, in which emissions are stabilized through concerted international action.

With the business-as-usual projections, the chance of a megadrought before century’s end was about 80 percent for both the Southwest and the Central Plains; with a serious effort at stabilization, it fell to the 60-70 percent range for the Central Plains but was essentially unchanged for the Southwest:

This desiccation is consistent across most of the models and moisture balance variables, indicating a coherent and robust drying response to warming. … Notably, future drought risk will likely exceed even the driest centuries of the Medieval Climate Anomaly (1100-1300 CE) in both future emissions scenarios, leading to unprecedented drought conditions.

Here’s how they think this century will look compared to the last millennium, with the brown line representing tree-ring data and the others representing three different metrics of available soil moisture, for the business-as-usual scenario:


For further reading, I can recommend good  coverage I found at Scientific American, Slate, National Geographic and the UK’s Guardian.

Comments (30)

  1. Submitted by Greg Kapphahn on 02/17/2015 - 10:22 am.

    It Seems Increasingly Likely

    that the questions from the 2050s on will be these:

    can we still grow crops in the US,…

    and WHERE?

    Meanwhile, the governments of the water rich states in the north central US (such as Minnesota),…

    had best be formulating policies regarding how much water we will share with the states whose populations will need it,…

    and whether the water to slake their thirst in the summer,…

    will cost them as much as the fuels required to heat our homes in the winter have cost us over the past many decades.

    We’d also better make sure that our representatives in the federal government create federal water policies very soon,…

    (BEFORE a water crisis develops),…

    policies that protect us from simply having our water resources nationalized and stolen right out from under us without compensation.

    • Submitted by Tom Anderson on 02/19/2015 - 09:19 pm.

      According to Governor Dayton

      Water belongs to us all which makes the statement “policies that protect us from simply having our water resources nationalized and stolen right out from under us without compensation” just not right. If you agree with the Governor.

  2. Submitted by Thomas Swift on 02/17/2015 - 10:53 am.

    Lake Mead is coming off several years of historically high water levels from the 1980’s through 2000. It is at a low also seen in 1955-58 and 1968, 69.

    The effects of warming are best seen in the massive influx of people moving to the South West in search of it.

  3. Submitted by Joe Smithers on 02/17/2015 - 10:53 am.

    doom and gloom

    Deserts were once oceans and vice versa. Records were made to be broken. The earth has always been constantly changing and we will just have to adapt to it. Cali has a drought and Boston has too much water (frozen though). Obviously we have some influence on global change but how much and if we can prevent change is questionable.

  4. Submitted by Ray Schoch on 02/17/2015 - 11:18 am.

    It’s the most valuable resource

    Water is the most valuable resource available – human life absolutely depends upon it – and those states bordering the Great Lakes have a huge advantage over other states should the most grim of these grim predictions come to pass.That is, they have a huge advantage if Greg Kapphahn’s last point is attended to.

    There are also local and intrastate water issues, specifically around who owns what in terms of water. This is an important point to consider when proposals like the PolyMet mining one are made. Just because a person or legal entity has the ability to draw water from a particular source doesn’t necessarily mean they are entitled to do so.

    Minneapolis, for example, currently has no backup water supply, and gets all its water from the Mississippi. A plan is in place to drill wells into local aquifers, which would be used to provide “emergency” water should the need arise because of some industrial accident or act of terror, but what if climate change dramatically alters the flow of the river – to the point where, to speculate, only half the current cubic feet per second (cusecs is the term I learned to refer to this) flows past the water intakes for the city? The “emergency” supply could quickly become, for a time, until the aquifers themselves dry up, part of the “normal” water supply.

    Who owns the water that would be brought up from underground to supply the city?

    For that matter, who owns the water that’s currently pumped from underground for agricultural use in parts of Minnesota right now?

    Colorado has a statement in its state constitution to the effect that “the waters of the state of Colorado belong to the people of Colorado,” and that statement drives a lot water-rights and related legal decision-making in the state.

    Who owns the waters of the state of Minnesota? I have yet to find anything in the state constitution that specifically spells out an answer to that question in the way the Colorado constitution does. Should “megadroughts” become a fact of life at some future point, it’s an answer that’s going to be crucial in multiple ways.

  5. Submitted by Tom Karas on 02/17/2015 - 12:15 pm.

    Great Lakes water

    In about 2007 I had the occasion to share some time with a county water commissioner from the Sierra Nevada section of California. We discussed the snowpack levels and then I asked him what he felt was to be the fate of Great Lakes water. “Feds will control it within 15 years” was his quick and succinct answer.
    Regardless of your affinity to Fox News for the reason, water will be the new oil and the battles will be ugly.

    • Submitted by Kurt Nelson on 02/17/2015 - 02:50 pm.


      The watershed for Lake Superior is surprisingly small for such a large body of water. The amount of water entering the lake just barely keeps up with evaporation, so as Minnesota grows warmer, and more and more water evaporates, the lower the lake level. No amount of government intervention will change that fact, unless of course they find a way to enlarge the watershed.

      • Submitted by Jim Halonen on 02/17/2015 - 03:23 pm.

        Current lake level

        You’re not aware that Lake Superior water level is at a 17 year high, with much of the gain in the last two years? This warming theory just never gets (real) legs.

        • Submitted by Kurt Nelson on 02/17/2015 - 04:25 pm.


          Except as you might remember, the lake froze last winter, which reduced overall evaporation, and there was good snowpack. This year, the lake will not freeze, and the snowpack is low so lets see if your “theory” holds any of that water.

          You may or may not believe in science, but if you do, you would know that warmth increases evaporation, and there is no dispute that Minnesota is getting warmer, so absent more moisture, the lake level will continue to fall, despite the good intentions of climate change deniers.

  6. Submitted by Thomas Swift on 02/17/2015 - 02:26 pm.

    Squirting tears is no solution to a perceived lack of water. Perceived I say, because all of the water that was ever on the Earth is still here. Droughts are a matter of logistics. Logistics is something humans do very well.

    If drought becomes a permanent thing in the South West (and there is no proof this is the case), I trust science and engineering to solve the problem.

    • Submitted by Tom Karas on 02/17/2015 - 02:59 pm.

      science by convenience

      What a humorous example of a belief in science. When the science fits, you will wear that shoe. When the science does not fit, it must not be real science. And just look at that long track record of engineers fixing droughts. Or do they have to be classified as permanent before the engineers get involved?

      • Submitted by Thomas Swift on 02/17/2015 - 03:46 pm.

        “Or do they have to be classified as permanent before the engineers get involved?”

        Remember hearing of the dustbowl? This too, shall pass, Tom.

      • Submitted by Thomas Swift on 02/17/2015 - 03:51 pm.

        Engineers. Fixing drought.

        Rational people will require a problem be incapable of resolving itself before mounting the effort to do so.

        Remember hearing about the “dustbowl”? This too, shall pass, Tom.

        • Submitted by jason myron on 02/17/2015 - 04:08 pm.

          Thar’s brilliant.

          I suppose when your car starts making a noise you wait and hope for it to resolve itself before taking it to the mechanic? That’s rational alright…

        • Submitted by Neal Rovick on 02/18/2015 - 08:10 am.

          Desalinating plant water is estimated to cost about $2000 per acre-foot (which will supply 2 families for a year), which is double what is presently paid for water.

          How does that work for agriculture?

          Not so good.

          It takes $ 750 of retail water to grow $ 150 of cotton (and that would be $ 1500 for desalinated water).

          Seems to me it is a “solution” with much pain embedded in it.

          • Submitted by Thomas Swift on 02/18/2015 - 08:38 am.

            We were paying triple the 1990 cost of a gallon of gasoline until a year ago. Please tell me more of this pain of which you speak.

            Oil is a consumable resource that is finite; water is finite, but is not consumable in that it is endlessly being naturally and artificially re-cycled.

            The largest cost of de-salinization, besides labor, is energy. Currently it takes about 14Kw hours of electricity per 1k water. That is 1/2 of what it took in 1978. Reverse Osmosis is no longer the only technology available, membrane systems take a fraction of the energy to operate.

            Agricultural Kings county and the greater San Fernando valley, California used to be the single largest consumer of potable water in the state. That is no longer true; it’s Los Angeles….all those people chasing global warming.

            • Submitted by Jonathan Ecklund on 02/18/2015 - 09:19 am.

              You are comparing gasoline with water? Water is an essential resource, necessary to sustain human life; you die in a few days without any. Gasoline is a refined petroleum product that is indeed a finite resource. As we burn more and more of it, we continue to damage the environment, which in turn affects global water storage patterns. Basically, climate change has a negative effect on fresh-water aquifers, and as is, only 2.5% of the water on planet Earth is freshwater. This loss of freshwater, plus the fact that we are moving into cities in the desert and diverting water there, AND the fact that the world population has tripled in the last 100 years AND the fact that 1/3 of the world’s population already experiences water scarcity, points to a huge looming problem with water, far worse than with oil.

              I think you should make some recordings for your great-grandchildren, so they can learn from the mistakes of history when the war for water comes to the US. You think people get irate when they have to spend 4 bucks for a gallon of gas? Wait until they have to spend 400 dollars for a drink of water. At least we’ll all be dead, but this is not something I want to bequeath to future generations.

              • Submitted by Thomas Swift on 02/18/2015 - 03:48 pm.

                Water is more important than gasoline, congratulations; you got it. Unfortunately, you missed the point of my response which was if we are willing to pay x3 cost for gasoline, why would anyone complain about higher prices for water?

                “Basically, climate change has a negative effect on fresh-water aquifers, and as is, only 2.5% of the water on planet Earth is freshwater. This loss of freshwater…”

                Again, every gallon of water that the Earth has ever contained is still here. There is no net loss of freshwater. The only effect a changing climate can have is the distribution. A matter of logistics, as I said.

                • Submitted by Jonathan Ecklund on 02/19/2015 - 04:51 pm.

                  Congratulations are not necessary

                  I was pointing out the inanity of comparing a basic necessity for human life to a non-renewable resource that damages our world through it’s very use.

                  And you are incorrect on your statement about ‘no net loss of freshwater.’ See: the hydrological cycle.

            • Submitted by Neal Rovick on 02/18/2015 - 10:52 am.

              Water used by agriculture?

              ….Approximately nine million acres of farmland in California are irrigated, representing roughly 80% of all human water use….. (2014)


              Try citing a source the next time you make claims like urban use being greater than agriculture.

              Tell me again how it works out if a crop uses $ 1500 dollars of water to grow what is now $ 150 worth of crops? Price hike anywhere in the future? Don’t need a crystal ball for that one.

              The agriculture model in California (and elsewhere) and food pricing only works based on essentially free, unlimited water.

    • Submitted by Todd Adler on 02/17/2015 - 05:45 pm.


      The water is indeed still on the planet, but much of it is in a form we can’t use. That means you have to take the salt out of it, which is expensive to do given current technology. It’s also not practical unless you live near a large body of water to draw from.

      Now you can just build large pipelines from the ocean inland, but that’s an additional engineering project that someone needs to pay for.

  7. Submitted by Jonathan Ecklund on 02/17/2015 - 04:19 pm.


    As someone who lived in New Mexico in the 90’s and aughts, and who is into all things archaeological, I should point out that use of the word ‘Anasazi’ is itself considered offensive to the Ancient Puebloan Peoples. Anasazi is a Navajo word for “enemies” or something less acceptable, and is what the Navajo used to refer to the Pueblo culture that there were at odds with. Basically, when white folks were asking the Navajo who these people were, they called them “enemies” (anasazi) and it stuck.

    It would be like if, sometime in the future, aliens came to the upper midwest (dare I say, the NORTH?), and asked all the surviving Minnesotans what the people to the east were called, and we said “Cheeseheads.”

  8. Submitted by Constance Sullivan on 02/18/2015 - 11:05 am.

    In Brazil, the huge of city of Sao Paolo is just about out of water. Not just from evaporation, but pollution and lack of rain (global warming effects). There’s water for people maybe a couple of hours per week. Per week. The reservoirs are drying up completely. Restaurants and hospitals can’t function, sanitation generally is disastrous.

    Check it out. That is the future of water emergencies due to global warming and our cavalier dependence on engineering to solve things when they’re past the point of solving, because of denial and governmental inaction.

    • Submitted by Thomas Swift on 02/19/2015 - 08:43 am.

      “São Paulo Water Crisis Linked to Growth, Pollution and Deforestation”

      “Officials say that drastic rationing may be needed, with water service provided only two days a week.”

      “May be needed…”

      “When it rains, it rains too much, and when there’s drought, it’s way too dry.”

      A cavalier dependence on engineering would lead to building more reservoirs to support the larger population…but it’s past solving because of denial and governmental inaction, probably.

      • Submitted by Neal Rovick on 02/19/2015 - 08:58 am.

        Gosh, where are the private sector solutions, Tom?

        • Submitted by Thomas Swift on 02/19/2015 - 03:56 pm.


          Looks like a monster investment opportunity, don’t it?

          • Submitted by Rachel Kahler on 02/19/2015 - 04:32 pm.

            Not really

            Aquafed believes, and requires its members to abide by, the core belief that clean water and sanitation access is a basic human right. If clean water and sanitation MUST be supplied to all human beings, it must be affordable to every person. In a world in which the wealth is owned by too few people, I don’t see that the provision of basic human rights will be a profitable one. That being said, I find it very interesting that this supposedly benevolent organization of private businesses includes the following in its code of ethics:

            “Governments must ensure progressively that the Right is effective for all individuals.”

            That is, if there is a profit to be made, Aquafed believes that taxpayers should pay for it. So, in a world of increasing wealth disparity, I would expect a higher cost to the rich than the poor–unless the rich are willing to forego the protections of a strong government for the sake of not paying for water for poor people.

            Somehow, Mr. Swift, I didn’t expect you to embrace such a concept.

          • Submitted by Jonathan Ecklund on 02/19/2015 - 04:34 pm.

            Monstrous, perhaps…

            It looks more like an enterprise that is designed to subjugate the poor by charging them for-profit rates for water.

            “Apart from intensive public relations efforts to present private water multinationals as part of the solution, AquaFed also dedicated substantial resources on monitoring the discussions taking place during the International Forum in Defense of Water, the civil society gathering that took place in parallel to the World Water Forum. This reflects the main reason for Suez and Veolia to establish AquaFed: the serious PR problems which these water multinationals face now that it becoming apparent that the high claims made of privatisation have not been fulfilled. During his time as CEO and chairman of the Ondeo Group (Suez’ water division) Gerard Payen (AquaFed president) orchestrated the company’s massive global expansion, including acquiring numerous water concessions in large cities in developing countries. The company’s promises have since turned sour and in the last few years, Suez has been forced to withdraw from concessions in cities in Bolivia, the Philippines, Argentina and elsewhere after failing to deliver promised improvements. Despite the PR budgets available to the water corporations, anti-privatisation activists are seen to be winning the public debate.”

            This can be reasonably linked to the Coachabamba protests in bolivia in 2000, which I well remember. The locals protested the privatization of water service in their town when their rates for water jumped dramatically.

            “The tensions erupted when a new firm, Aguas del Tunari – a joint venture involving Bechtel – was required to invest in construction of long-envisioned dam (a priority of Mayor Manfred Reyes Villa) – so they had dramatically raised water rates.”

            “On April 10, 2000, the national government reached an agreement with the Coordinadora to reverse the privatization. A complaint filed by foreign investors was resolved by agreement in January 2006.”

            Aquafed was founded in 2005, around when this case was coming to a conclusion.

  9. Submitted by cory johnson on 02/22/2015 - 06:20 pm.

    population growth….

    Is the main enemy of keeping water plentiful and cheap. Until we seriously address it we cannot seriously expect to keep from becoming an expensive traded commodity.

  10. Submitted by Ben Munroe on 02/24/2015 - 03:56 pm.

    Economic growth, health and population

    Except that economic growth and lower child mortality are correlated with lower birth rates. Malthusian arguments just don’t hold water.

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