Heat, Not Just Rainfall, Plays into New Projections
Increasing heat is expected to extend dry conditions to far more farmland and cities by the end of the century than changes in rainfall alone, says a new study. Much of the concern about future drought under global warming has focused on rainfall projections, but higher evaporation rates may also play an important role as warmer temperatures wring more moisture from the soil, even in some places where rainfall is forecasted to increase, say the researchers.
The study is one of the first to use the latest climate simulations to model the effects of both changing rainfall and evaporation rates on future drought. Published this month in the journal Climate Dynamics, the study estimates that 12 percent of land will be subject to drought by 2100 through rainfall changes alone; but the drying will spread to 30 percent of land if higher evaporation rates from the added energy and humidity in the atmosphere is considered.
An increase in evaporative drying means that even regions expected to get more rain, including important wheat, corn and rice belts in the western United States and southeastern China, will be at risk of drought. The study excludes Antarctica.
“We know from basic physics that warmer temperatures will help to dry things out,” said the study’s lead author, Benjamin Cook, a climate scientist with joint appointments at Columbia University’s Lamont-Doherty Earth Observatory and the NASA Goddard Institute for Space Studies. “Even if precipitation changes in the future are uncertain, there are good reasons to be concerned about water resources.”
In its latest climate report, the International Panel on Climate Change (IPCC) warns that soil moisture is expected to decline globally and that already dry regions will be at greater risk of agricultural drought. The IPCC also predicts a strong chance of soil moisture drying in the Mediterranean, southwestern United States and southern African regions, consistent with the Climate Dynamics study.
Using two drought metric formulations, the study authors analyze projections of both rainfall and evaporative demand from the collection of climate model simulations completed for the IPCC’s 2013 climate report. Both metrics agree that increased evaporative drying will probably tip marginally wet regions at mid-latitudes like the U.S. Great Plains and a swath of southeastern China into aridity. If precipitation were the only consideration, these great agricultural centers would not be considered at risk of drought. The researchers also say that dry zones in Central America, the Amazon and southern Africa will grow larger. In Europe, the summer aridity of Greece, Turkey, Italy and Spain is expected to extend farther north into continental Europe.
“For agriculture, the moisture balance in the soil is what really matters,” said study coauthor Jason Smerdon, a climate scientist at Lamont-Doherty. “If rain increases slightly but temperatures also increase, drought is a potential consequence.”
Today, while bad weather periodically lowers crop yields in some places, other regions are typically able to compensate to avert food shortages. In the warmer weather of the future, however, crops in multiple regions could wither simultaneously, the authors suggest. “Food-price shocks could become far more common,” said study coauthor Richard Seager, a climate scientist at Lamont-Doherty. Large cities, especially in arid regions, will need to carefully manage their water supplies, he added.
The study builds on an emerging body of research looking at how evaporative demand influences hydroclimate. “It confirms something we’ve suspected for a long time,” said Toby Ault, a climate scientist at Cornell University, who was not involved in the study. “Temperature alone can make drought more widespread. Studies like this give us a few new powerful tools to plan for and adapt to climate change.”
Rainfall changes do not tell the whole story, agrees University of New South Wales researcher Steven Sherwood, in a recent Perspectives piece in the leading journal Science. “Many regions will get more rain, but it appears that few will get enough to keep pace with the growing evaporative demand.”
The authors have made all their data and calculations public available on a supplementary website.
All you people falling for such an obvious April Fool prank. You missed the punch line at the end: “The authors have made all their data and calculations public available on a supplementary website.”
(not sure if /sarc is appropriate here…)
Jimbo, how/where do you find all these wonderful abstracts?
By 1985, air pollution will have reduced the amount of sunlight reaching earth by one half…” Life magazine, January 1970.
Get a good grip on your long johns, cold weather haters–the worst may be yet to come. That’s the long-long-range weather forecast being given out by “climatologists.” the people who study very long-term world weather trends…. Washington Post January 11, 1970
Because of increased dust, cloud cover and water vapor “…the planet will cool, the water vapor will fall and freeze, and a new Ice Age will be born,” Newsweek magazine, January 26, 1970.
In ten years all important animal life in the sea will be extinct. Large areas of coastline will have to be evacuated because of the stench of dead fish. — Paul Ehrlich, Earth Day (1970)
“Civilization will end within 15 or 30 years unless immediate action is taken against problems facing mankind. We are in an environmental crisis which threatens the survival of this nation, and of the world as a suitable place of human habitation,” – Barry Commoner Washington University Earth Day 1970
“(By 1995) somewhere between 75 and 85 percent of all the species of living animals will be extinct.” Sen. Gaylord Nelson, quoting Dr. S. Dillon Ripley, Look magazine, April 1970.
“By the year 2000…the entire world, with the exception of Western Europe, North America and Australia, will be in famine,” Peter Gunter, North Texas State University, The Living Wilderness, Spring 1970.
Convection in the Antarctic Ice Sheet Leading to a Surge of the Ice Sheet and Possibly to a New Ice Age. – Science 1970
“In the next 50 years fine dust that humans discharge into the atmosphere by burning fossil fuel will screen out so much of the sun’s rays that the Earth’s average temperature could fall by six degrees. Sustained emissions over five to 10 years, could be sufficient to trigger an ice age.” – Washington Post – July 9, 1971
“By the year 2000 the United Kingdom will be simply a small group of impoverished islands, inhabited by some 70 million hungry people … If I were a gambler, I would take even money that England will not exist in the year 2000.” Paul Ehrlich 1971
New Ice Age Coming—It’s Already Getting Colder. Some midsummer day, perhaps not too far in the future, a hard, killing frost will sweep down on the wheat fields of Saskatchewan, the Dakotas and the Russian steppes…..Los Angles Times Oct 24, 1971
The latest computer generated climate simulations say “no”, again. No rain that is. Well, Eastern Australia is now enjoying a record wet season with rivers and dams full. It looks like yet another Global Warming prediction fail. They need to start shouting louder.
John F. Hultquis
In this madness is the method.
Hamlet.
Meanwhile in the real world.
They could easily have found a stock photo of drought ravaged corn for their cover photo. Instead they just used a picture of corn stubble left after what was probably a record harvest.
‘If” a mini ice age or full glacial will arrive, it is true there is less evaporation and less rainfall in some regions. Nothing to do with heat, tropical regions naturally being more humid get more rain.
Our oceans provide the most evaporation, and galactic sub atomic particles help form more cloud and rain. Sun activity can of course deflect these. Should water freeze there is no evaporation, i.e. more glaciers and polar encroachments. The monsoon areas might shift?
Production for profit, for amassing wealth in few hands and let billions of humans starve, accelerates climate deterioration!
I wonder just what kk16085 does for self sustenance; of course using NOTHING made available by ANY for profit entity ??
So we now have seven of those billions of humans; how many of those seven billions died in the most recent 30 year climate cycle due to starvation caused by “for profit” entities ??
Benjamin Cook et al
Farmers don’t dance for rain. Modern agriculture depends on man-made irrigation. In very warm climates, water at the surface evaporates but most rainwater penetrates the soil and become groundwater. Excluding glaciers, groundwater accounts for 98% of fresh water. Only 2% are in the surface including lakes, rivers and swamps. Increasing rainfall replenishes the groundwater. This is a common source of water for irrigation.
Assuming severe global warming, the permafrost in Siberia, Northern China, Mongolia, Canada, Alaska and Greenland will melt and the land will become productive. These regions will have a golden age of agriculture.
“Warming Climate May Spread Drying to a Third of Earth, Says Study”
Don’t these fools know that over 70% of the earth is covered in WATER? That we have a continent completely covered in ICE? Not to mention vast parts of mountain ranges (as well as Greenland) also covered in ice?
So they are saying the entire world (not covered in water and ice) is going to be a giant Sahara desert….
They owe me a new clean computer monitor and key board….