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OKIsItJustMe

(19,933 posts)
Thu Feb 12, 2015, 09:30 PM Feb 2015

Warming Pushes Western U.S. Toward Driest Period in 1,000 Years

http://www.earth.columbia.edu/articles/view/3232
[font face=Serif][font size=5]Warming Pushes Western U.S. Toward Driest Period in 1,000 Years[/font]
[font size=4]Study Warns of Unprecedented Risk of Drought in 21st Century[/font]
2015-02-12

[font size=3]During the second half of the 21st century, the U.S. Southwest and Great Plains will face persistent drought worse than anything seen in times ancient or modern, with the drying conditions “driven primarily” by human-induced global warming, a new study predicts.

The research says the drying would surpass in severity any of the decades-long “megadroughts” that occurred much earlier during the past 1,000 years—one of which has been tied by some researchers to the decline of the Anasazi or Ancient Pueblo Peoples in the Colorado Plateau in the late 13th century. 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.”

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http://mediarelations.cornell.edu/2015/02/12/megadrought-likely-for-western-u-s-by-end-of-century/
[font face=Serif][font size=5]‘Megadrought’ likely for western U.S. by end of century[/font]
February 12, 2015 By Melissa Osgood

[font size=3]The consequences of climate change paint a bleak picture for the Southwest and much of America’s breadbasket, the Great Plains. A “megadrought” likely will occur late in this century, and it could last for three decades, according to a new report by Cornell University and NASA researchers in the journal Science Advances, published today.

“The results were striking. As a society, we’ve weighted the dice toward megadrought. Data clearly point to a high risk in the Southwest and Great Plains, as we continue to add carbon dioxide into our atmosphere,” said Toby Ault, Cornell associate professor of earth and atmospheric sciences. “However, if we manage to get serious about lowering greenhouse gases within the next 10 years, we could face a lower risk.”

With a drier future and higher regional temperatures amplifying possible late-century droughts, the situation presents a major adaptation challenge for managing the region’s water needs, explains Ault, who along with lead author Benjamin Cook and Jason Smerdon, both of NASA, published their new study, “Unprecedented 21st Century Drought Risk in the American Southwest and Central Plains Drought Risk in Western North America.”

By examining tree rings and other physical clues, previous research had identified a period of time called Medieval Climate Anomaly – from the year 1100 to the year 1300 – when megadroughts were more common. By analyzing data from 17 state-of-the-art global climate models, the researchers learned that western North America’s future drought risk exceeded even the driest centuries of the Medieval Climate Anomaly.

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http://www.nasa.gov/press/2015/february/nasa-study-finds-carbon-emissions-could-dramatically-increase-risk-of-us/index.html
[font face=Serif]
February 12, 2015
RELEASE 15-020
[font size=5]NASA Study Finds Carbon Emissions Could Dramatically Increase Risk of U.S. Megadroughts[/font]
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NASA scientists used tree rings to understand past droughts and climate models incorporating soil moisture data to estimate future drought risk in the 21st century.
Image Credit: NASA's Goddard Space Flight Center
Download this video in HD formats from Goddard's Scientific Visualization Studio.[/font]

[font size=3]Droughts in the U.S. Southwest and Central Plains during the last half of this century could be drier and longer than drought conditions seen in those regions in the last 1,000 years, according to a new NASA study.

The study, published Thursday in the journal Science Advances, is based on projections from several climate models, including one sponsored by NASA. The research found continued increases in human-produced greenhouse gas emissions drives up the risk of severe droughts in these regions.

"Natural droughts like the 1930s Dust Bowl and the current drought in the Southwest have historically lasted maybe a decade or a little less," said Ben Cook, climate scientist at NASA's Goddard Institute for Space Studies and the Lamont-Doherty Earth Observatory at Columbia University in New York City, and lead author of the study. "What these results are saying is we're going to get a drought similar to those events, but it is probably going to last at least 30 to 35 years."

[font size=1]North American map of estimated ground moisture in 2095 based on a moderate emissions scenario

Soil moisture 30 cm below ground projected through 2100 for moderate emissions scenario RCP 4.5. The soil moisture data are standardized to the Palmer Drought Severity Index and are deviations from the 20th century average.
Image Credit: NASA's Goddard Space Flight Center
Download this video in HD format from Goddard's Scientific Visualization Studio.[/font]

According to Cook, the current likelihood of a megadrought, a drought lasting more than three decades, is 12 percent. If greenhouse gas emissions stop increasing in the mid-21st century, Cook and his colleagues project the likelihood of megadrought to reach more than 60 percent.

However, if greenhouse gas emissions continue to increase along current trajectories throughout the 21st century, there is an 80 percent likelihood of a decades-long megadrought in the Southwest and Central Plains between the years 2050 and 2099.

The scientists analyzed a drought severity index and two soil moisture data sets from 17 climate models that were run for both emissions scenarios. The high emissions scenario projects the equivalent of an atmospheric carbon dioxide concentration of 1,370 parts per million (ppm) by 2100, while the moderate emissions scenario projects the equivalent of 650 ppm by 2100. Currently, the atmosphere contains 400 ppm of CO2.

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