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Excerpt: "It is increasingly clear that we already live in the era of human-induced climate change, with a growing frequency of weather and climate extremes like heat waves, droughts, floods and fires."

Dried lake sediment, left behind by a shrinking lake at Wooly Hollow State Park, Arkansas. (photo: John Lewis/National Weather Service)
Dried lake sediment, left behind by a shrinking lake at Wooly Hollow State Park, Arkansas. (photo: John Lewis/National Weather Service)

Hundred-Year Forecast: Drought

By Christopher R. Schwalm, Christopher A. Williams, Kevin Schaefer, The New York Times

12 August 12


Y many measurements, this summer's drought is one for the record books. But so was last year's drought in the South Central states. And it has been only a decade since an extreme five-year drought hit the American West. Widespread annual droughts, once a rare calamity, have become more frequent and are set to become the "new normal."

Until recently, many scientists spoke of climate change mainly as a "threat," sometime in the future. But it is increasingly clear that we already live in the era of human-induced climate change, with a growing frequency of weather and climate extremes like heat waves, droughts, floods and fires.

Future precipitation trends, based on climate model projections for the coming fifth assessment from the Intergovernmental Panel on Climate Change, indicate that droughts of this length and severity will be commonplace through the end of the century unless human-induced carbon emissions are significantly reduced. Indeed, assuming business as usual, each of the next 80 years in the American West is expected to see less rainfall than the average of the five years of the drought that hit the region from 2000 to 2004.

That extreme drought (which we have analyzed in a new study in the journal Nature-Geoscience) had profound consequences for carbon sequestration, agricultural productivity and water resources: plants, for example, took in only half the carbon dioxide they do normally, thanks to a drought-induced drop in photosynthesis.

In the drought's worst year, Western crop yields were down by 13 percent, with many local cases of complete crop failure. Major river basins showed 5 percent to 50 percent reductions in flow. These reductions persisted up to three years after the drought ended, because the lakes and reservoirs that feed them needed several years of average rainfall to return to predrought levels.

In terms of severity and geographic extent, the 2000-4 drought in the West exceeded such legendary events as the Dust Bowl of the 1930s. While that drought saw intervening years of normal rainfall, the years of the turn-of-the-century drought were consecutive. More seriously still, long-term climate records from tree-ring chronologies show that this drought was the most severe event of its kind in the western United States in the past 800 years. Though there have been many extreme droughts over the last 1,200 years, only three other events have been of similar magnitude, all during periods of "megadroughts."

Most frightening is that this extreme event could become the new normal: climate models point to a warmer planet, largely because of greenhouse gas emissions. Planetary warming, in turn, is expected to create drier conditions across western North America, because of the way global-wind and atmospheric-pressure patterns shift in response.

Indeed, scientists see signs of the relationship between warming and drought in western North America by analyzing trends over the last 100 years; evidence suggests that the more frequent drought and low precipitation events observed for the West during the 20th century are associated with increasing temperatures across the Northern Hemisphere.

These climate-model projections suggest that what we consider today to be an episode of severe drought might even be classified as a period of abnormal wetness by the end of the century and that a coming megadrought - a prolonged, multidecade period of significantly below-average precipitation - is possible and likely in the American West.

The current drought plaguing the country is worryingly consistent with these expectations. Although we do not attribute any single event to global warming, the severity of both the turn-of-the-century drought and the current one is consistent with simulations accounting for warming from increased greenhouse gases. The Northern Hemisphere has just recorded its 327th consecutive month in which the temperature exceeded the 20th-century average. This year had the fourth-warmest winter on record, with record-shattering high temperatures in March. And 2012 has already seen huge wildfires in Colorado and other Western states. More than 3,200 heat records were broken in June alone.

And yet that may be only the beginning, a fact that should force us to confront the likelihood of new and painful challenges. A megadrought would present a major risk to water resources in the American West, which are distributed through a complex series of local, state and regional water-sharing agreements and laws. Virtually every drop of water flowing in the American West is legally claimed, sometimes by several users, and the demand is expected to increase as the population grows.

Many Western cities will have to fundamentally change how they acquire and use water. The sort of temporary emergency steps that we grudgingly adopt during periods of low rainfall - fewer showers, lawn-watering bans - will become permanent. Some regions will become impossible to farm because of lack of irrigation water. Thermoelectric energy production will compete for limited water resources.

There is still time to prevent the worst; the risk of a multidecade megadrought in the American West can be reduced if we reduce fossil-fuel emissions. But there can be little doubt that what was once thought to be a future threat is suddenly, catastrophically upon us. your social media marketing partner


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0 # MidwestTom 2012-08-12 09:31
There is some interesting research from Europe concerning the effect of vapor trails on climate. In a nutshell their research has indicated that increases in vapor trails results in less rain.
+15 # Billy Bob 2012-08-12 13:57
There's also been some research into the idea that carbon emissions from the burning of fossil fuel is causing global climate change. This would account for the drought in a tangible way that doesn't require vapor trails.

But hey! if you can find another study saying it's caused by kids not eating their vegetables, I'm sure that would also be preferable to dealing with the bitter pill that we have to stop using oil, coal and natural gas.
+2 # JSRaleigh 2012-08-13 09:42
Quoting MidwestTom:
There is some interesting research from Europe concerning the effect of vapor trails on climate. In a nutshell their research has indicated that increases in vapor trails results in less rain.

Has there been any interesting research into who profits from promoting such pseudo-science obfuscation?
+12 # brianf 2012-08-12 10:44
Scientists who looked at the past predicted years ago that global warming would bring mega-droughts to the SouthWest and turn the Great Plains into a desert. This is what happened the last time global temperatures were only a little warmer than they are now. Models still have not caught up with paleoclimatolog y because they don't include all the feedbacks. I wish scientists would pay more attention to what actually happened in the past.

The authors of this article don't even mention the worst effect of the coming megadroughts, desertification , and other products of global warming: food shortages. This year's drought will bring higher food prices and some hunger. But in the future we will have worldwide famine. Then we will take global warming seriously, but it will be too late to save billions from suffering and early death.
+14 # VoiceofReason613 2012-08-12 10:55
Yes, and this is why it is scandalous that at a time when already an estimated 20 million people are dying annually from hunger and its effects and almost a billion people are chronically hungry, 70% of the grain produce in the US and about 40% of the grain produced worldwide are fed to animals destined for slaughter. As president of Jewish vegetarians of North America I also want to point out that animal-based diets also contribute significantly to climate change, deforestation, soil erosion, rapid species losses, and other environmental threats and also use far more water, energy, and other resources than do plant-based diets. Time to end the madness and sheer insanity and shift to plant-based diets to help shift our imperiled planet to a sustainable path.
+4 # Glen 2012-08-12 10:59
Interesting, brianf. As I was reading your post I was discussing droughts and increasing desert regions in various parts of the world, with a friend. The dry lakes and enlarged deserts and human destruction of forests, not to mention moving herds of animals that decimate local flora, are not discussed as they were even two years ago. Now that the U.S. is experiencing similar effects of warming, I wonder how long published reports and discussion will last in this country.
+4 # Glen 2012-08-12 11:05
My greatest worry is related to the last two paragraphs of this article: the acquisition of water by states in dire need. There are states such as Arkansas that have much water underground and that water has been desired by Texas for many years. How about the lakes and streams in other states? And their underground systems.

To satisfy the needs of the many who overuse water, the clean and plentiful water of others will be sucked dry. If Arizona, et al., continue to build unnecessary suburbs, they should also require members to a serious limitation of water.
+3 # Billy Bob 2012-08-12 14:00
Including millions of Americans if we don't do something about it NOW. I believe neo-conservativ es in our government are already assuming it will come to that. That's why we "NEEDED" the "patriot" act, and to end Posse Comitatus.
+2 # Glen 2012-08-13 08:10
Billy, there will be war. There has already been skirmishes out west concerning opening wells, spillways, and similar. Water wars were predicted a long time ago, of course, but we now see that prediction come to pass.

The states surrounding the Great Lakes have signed an agreement to not release lake water, other states could protect their water the same way. As you say, it must be done NOW.
+2 # Billy Bob 2012-08-13 17:39
Obviously the Pentagon is already prepared to go to war against the U.S. citizens.
+2 # dick 2012-08-12 12:26
I wish that Obama, instead of BEGGING the inmates of the asylum to enter into bipartisan negotiations on the institutions budget, had used his amazing oratorical skills to EXPLAIN why we needed a TRANSFORMATIVE $timulus to put American to WORK on the infrastructure for a Changing Climate. MASSIVE reductions in traditional energy consumption, energy independence, etc. Ex., Subdividing, energy retrofitting, redesigning foreclosed McMansions. If a crisis is a terrible thing to waste, Obama inexcusably wasted 2: massive underemployment (& under-education )+Radical Climate Change. He sold EVERYTHING, EVERYONE out to Wall St. just to get a wee trickle of 19% credit put back on the cards. Goldman Sachs trickle down: worse than W's.
+11 # Billy Bob 2012-08-12 14:02
Because conservatives own most of the media and don't want you to think about climate change. If it gets to the point that they're forced to admit it, they'll blame THAT on Democrats as well.
+4 # reiverpacific 2012-08-13 20:26
There goes the tiny "Goldilocks Zone" we are so lucky to occupy and which sustains life -but we seem determined to shit in our own nest for short-term profit.
And just watch prices shoot up on everything from gas, to meat and all corn-based materials, so that the power-mongers can have their rarified air and climate-control led yachts, jets and mansions. But they have to eat, crap and breath the same air as us eventually.
And they still won't look at hemp!
+1 # mdhome 2012-08-13 23:28
50 years ago we had stockpiles of grain in storage, then they figured it cost too much and put a downward pressure on prices, now they have gotten rid of the government stockpiles and we now live hand to mouth and will be seeing the danger of not having a rainy day reserve.
+1 # Billy Bob 2012-08-15 17:16
Fifty years ago our government and most of our population were adults. Most of those adults had lived through tough times and realized things can always get worse again. They were concerned with their community and not just with themselves.

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