US Southwest faces threat of megadroughts with rising temps

October 5, 2016 by Alicia Chang
In this May 18, 2015 file photo, irrigation pipes sit along a dry irrigation canal on a field farmed by Gino Celli, who relies on senior water rights to water his crops, near Stockton, Calif. New research published on Wednesday, Oct. 5, 2016 found that increasing temperatures will greatly increase the risk of megadroughts in the Southwest region of the U.S. Oppressive dry spells lasting at least two decades have gripped the Southwest before, but scientists said future megadroughts would be hotter and more severe, putting a strain on water resources. (AP Photo/Rich Pedroncelli, File)

Already dealing with parched conditions, the U.S. Southwest faces the threat of megadroughts this century as temperatures rise, says a new study that found the risk is reduced if heat-trapping gases are curbed.

Oppressive dry spells lasting at least two decades have gripped the Southwest before, but scientists said future megadroughts would be hotter and more severe, putting a strain on water resources.

The study, published Wednesday in the journal Science Advances, is the latest to find that droughts more extreme than what is currently being experienced could become more common as the planet warms.

Using computer modeling, researchers calculated there's between a 70 percent and 90 percent chance the Southwest will experience a megadrought later this century.

If precipitation is below normal, the risk jumps to 99 percent—"virtually certain," said lead researcher Toby Ault of Cornell University.

If countries follow through with the Paris climate agreement to reduce emissions from the burning of coal, natural gas and oil to limit global temperature rise to well below 2 degrees Celsius (3.6 degrees Fahrenheit), then the risks are cut nearly in half, according to calculations.

"The likelihood of a megadrought is already increasing, and that risk will continue to go up as long as temperatures keep rising," Ault said in an email.

The Colorado River basin, which spans parts of Arizona, California, Colorado, New Mexico, Nevada, Utah, Wyoming and Mexico, has been in the midst of a historic drought for the past 16 years. Lake Mead is now surrounded by a distinctive white mineral "bathtub ring" showing the 130-foot drop in water levels since the beginning of the regional drought.

California, which is entering a sixth year of exceptional dryness, imposed mandatory statewide cuts on water usage last year that left brown lawns and fallowed fields. Restrictions have since eased with local water districts taking control of conservation efforts. On Wednesday, state regulators said some water districts are not conserving enough.

The new forecasts of a future megadrought are "scary for sure," said Jonathan Overpeck, a University of Arizona climate scientist who wasn't involved in the research.

Based on studies of tree rings and other data, past megadroughts in the Southwest have lasted between 20 to 35 years, depending on the location.

"It is important to realize that future droughts will be much hotter, and thus the impacts of these droughts will be much more severe," Overpeck said in an email.

Explore further: Dry soil to absorb some snowmelt heading to Colorado River

More information: Relative impacts of mitigation, temperature, and precipitation on 21st-century megadrought risk in the American Southwest, Science Advances  05 Oct 2016: Vol. 2, no. 10, e1600873, DOI: 10.1126/sciadv.1600873 , http://advances.sciencemag.org/content/2/10/e1600873

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12 comments

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aksdad
1.7 / 5 (11) Oct 05, 2016
This isn't a scientific study, it's policy advocacy to reduce CO2 emissions. How do I know? This line from the study:

An aggressive reduction in global greenhouse gas emissions cuts megadrought risks nearly in half.


How do they know that? They use computer-generated Global Circulation Models that have been specifically tuned to show that CO2 emissions warm the earth. How accurate are they? Not. See here from IPCC AR5:

http://www.climat...g1-4.jpg

The models all overestimate warming. This is a great line from the study:

Although some studies have relied on precipitation alone to identify prolonged drought or megadrought conditions, our results show that this approach tends to underestimate risk in a changing climate


News flash: precipitation (rain/snow) defines a drought. That's it. One good winter of snowfall can end a severe drought. It is weather patterns that affect drought, not warming.
antigoracle
1.4 / 5 (9) Oct 05, 2016
Using computer modeling

Mega millions squandered on Mega AGW Cult lies.
Mark Thomas
4.4 / 5 (7) Oct 05, 2016
Sounds like the biblical plagues on Egypt. According to the bible, the Pharaoh had to get smacked upside the head by ten different plagues until he finally realized he was wrong.

I wonder if any of the AGW Deniers in Louisiana who got flooded out this year in a global warming intensified storm were having second thoughts as they paddled away from their homes. If they keep rationalizing, e.g., "The models all overestimate warming," and labeling, "Mega AGW Cult lies," the rest of us will get to see just how much punishment they can take before they finally crack. How many freak storms, how many tornadoes, how many droughts, how many new high temperature records will it take before they are forced to admit something has changed? Will they be able to keep denying global warming as their gulf coast homes slide under the waves?
antigoracle
1.8 / 5 (5) Oct 05, 2016
How many freak storms, how many tornadoes, how many droughts, how many new high temperature records will it take before they are forced to admit something has changed?

So, it is true, you can't keep a Chicken Little retard down. How many times must we beg for you to find someone with a brain to explain the facts to you?
Have a gander at US drought history, take notice of the 1930s and 50s.
https://en.wikipe...2011.png
Trust me, your stupidity will be the end of you, long before any home slides under the waves.
Shootist
1.8 / 5 (5) Oct 05, 2016
Time to build 100 1000 megawatt fission plants to power a multitude of desalination facilities and to keep the lights of. The people that benefit from all this (California) must needs pay for it.
Bongstar420
3 / 5 (4) Oct 05, 2016
LOL...it happened in the past and it will happen in the future..but WORSE because of your damned hummer and those evil tomatoes you insist on eating
Anonym
1 / 5 (4) Oct 09, 2016
Droughts lasting centuries have occurred in the Southwest, according to tree-ring data, the last megadrought being about 1000 years ago. Clearly this study is simply more AGW scare-mongering --- and it's all scare-mongering from the "settled science" cabal: Arctic ice has not disappeared as it was supposed to by now; storm frequency is way down (Matthew the first big hurricane in over 10 years); severe weather events have decreased; acceleration of rising temps stalled in the late '90s, the claimed "record heat" of the past two years is an artifact of a strong El Nino (which they NEVER acknowledge) + manipulation of the temperature records.

How anyone can believe the errant nonsense cooked up by crony capitalists, their captive scientists and their media whores is almost as incomprehensible as anyone supporting the GOP misogynist-in-chief.

Yet they do.
TheGhostofOtto1923
5 / 5 (1) Oct 09, 2016
Sounds like the biblical plagues on Egypt. According to the bible, the Pharaoh had to get smacked upside the head by ten different plagues until he finally realized he was wrong
But god likes deserts as they are good places for wandering tribes of chosen people and messiahs for tempting by Satan. Hard to phrase that properly oh well.

"It is better to live in a desert land Than with a contentious and vexing woman" -trump1:11
Time to build 100 1000 megawatt fission plants to power a multitude of desalination facilities and to keep the lights of. The people that benefit from all this (California) must needs pay for it
What, with all that flat sunny wasteland? Carpet it with PV. The drier the better.
antigoracle
1 / 5 (2) Oct 09, 2016
1930s Dust Bowl Drought – and Current California Drought – Caused By Warm Ocean Anomalies

http://www.washin...ies.html
cantdrive85
1 / 5 (3) Oct 09, 2016
Oddly enough, this year which is the hottest ever (apparently), has been relatively mild and very wet here in central Arizona. But who cares about facts, it's only valid if it supports the AGWites fanciful beliefs.
Zzzzzzzz
4.7 / 5 (3) Oct 09, 2016
Deniers are psychotic delusional dumb pharks. It is a waste of time interfacing with them in any way. They bring zero value to any proposition. Zero value = worthless. The zero value judgement is too kind, due to the fact that they actually bring negative value. Negative value dumb pharks aren't wanted or needed. Indeed they are a serious lability. This only ends one way.......
Mark Thomas
5 / 5 (1) Oct 10, 2016
"has been relatively mild and very wet here in central Arizona"

I suppose you consider 97 degrees F and zero rain in the 10 day forecast to be mild and wet. Others might call that hot and dry you know.

http://intellicas...USAZ0166

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