. Earth Science News .
NASA Study Finds Warmer Future Could Bring Droughts

File photo of a drought affected river bed in the USA.
by Staff Writers
New York NY (SPX) Feb 13, 2007
NASA scientists may have discovered how a warmer climate in the future could increase droughts in certain parts of the world, including the southwest United States. The researchers compared historical records of the climate impact of changes in the sun's output with model projections of how a warmer climate driven by greenhouse gases would change rainfall patterns. They found that a warmer future climate likely will produce droughts in the same areas as those observed in ancient times, but potentially with greater severity.

"These findings strongly suggest that greenhouse gases and long-term changes in solar activity both can have major influences on climate via similar processes," said Drew Shindell, NASA Goddard Institute for Space Studies, New York. Shindell is lead author of a paper that appeared in the Dec. 27, 2006, issue of the American Geophysical Union's "Geophysical Research Letters."

"There is some evidence that rainfall patterns already may be changing," Shindell added. "Much of the Mediterranean area, North Africa and the Middle East rapidly are becoming drier. If the trend continues as expected, the consequences may be severe in only a couple of decades. These changes could pose significant water resource challenges to large segments of the population."

Using the NASA Goddard Institute for Space Studies climate model, researchers found that changes in solar output in the ancient past increased surface warming and altered atmospheric moisture and circulations. These changes likely led to the severe droughts seen in paleoclimate records.

The same model showed that greenhouse-gas warming has similar effects on the atmosphere, suggesting drier conditions may become more common in the subtropics.

Rainfall could decrease further in already water-stressed regions such as the southwest United States, Mexico, parts of North Africa, the Middle East, and Australia. Meanwhile, precipitation may increase across the western Pacific, along much of the equator and in parts of southeast Asia.

The computer model considers changes in the oceans, weather, and chemistry of the atmosphere, like ozone concentrations, and accurately reproduced the broad rainfall shifts toward regionally drier or wetter conditions during the past several hundred years.

Sunspot and ice core data also link the historical rainfall shifts to variations in the amount of energy released by the sun. Since the size of solar changes is uncertain, the study focused on the location and pattern of precipitation shifts, not their precise amount.

Increases in solar output break up oxygen molecules, raising ozone concentrations in the upper atmosphere. This adds to upper atmospheric heating that leads to shifts in circulations down to the surface.

In turn, surface temperatures warm, and the Earth's basic rainfall patterns are enhanced. For instance, in wet regions such as the tropics, precipitation usually increases, while dry areas become more prone to drought since rainfall decreases and warmer temperatures help remove the small amount of moisture in the soil.

"Precipitation is hard to predict because it is so highly variable, but these results increase our confidence that continued warming will be associated with large-scale changes in rainfall," said Shindell.

Researchers also considered numerous tree-ring, fire, and lake sediment records from across the Americas, including Mexico, Peru, and the Yucatan Peninsula.

These data are reliable indicators of historical climate and confirm a pronounced increase in drought frequency in the southern United States, Mexico, and other subtropical locations during periods of increased solar output in the past 1,200 years.

This long-term record of solar output is based on chemical isotopes whose production is related to the sun's brightness. Conversely, in parts of the tropics, ocean sediment data, key indicators of precipitation changes, reflect increased rainfall.

According to the researchers, the same processes identified by this new research very likely also affected past civilizations, such as the Pueblo people of New Mexico and Arizona who abandoned cities in the 1300s.

Email This Article

Related Links
Water, Water Everywhere and Not A Drop To Drink...
Goddard Institute for Space Studies
Water, Water Everywhere and Not A Drop To Drink...

3D Seismic Model Of Vast Water Reservoir Revealed
St. Louis MO (SPX) Feb 13, 2007
Seismologists at Washington University in St. Louis have made the first 3-D model of seismic wave damping - diminishing - deep in the Earth's mantle and has revealed the existence of an underground water reservoir at least the volume of the Arctic Ocean. It is the first evidence for water existing in the Earth's deep mantle.







  • Health Problems Hit Indonesia Flood Victims
  • Japan Launches Alert System For Tsunamis And Missiles
  • Catastrophe Bonds A Market Answer To Hail Or High Water
  • Call To Move Indonesian Capital After Deadly Floods

  • Global Warming Debate Heats Up In Washington
  • Study Shows Largest North America Climate Change In 65 Million Years
  • White House Issues Rare Letter Defending Record On Warming
  • From Greenhouse To Icehouse: New Clues On Ancient Climate Shift

  • Gascom To Launch 4 Smotr Low-Orbit Remote Sensing Satellites
  • GeoEye Makes Final Debt Payment For The Purchase Of Space Imaging
  • Google Earth To Blur Key India Sites
  • Brazilian Satellite Undergoes Environmental Tests

  • Cold Storage Solution For Global Warming
  • Energy Giant Total To Test Scheme To Store Carbon Emissions
  • Chinese firms win 1.46 bln dollar hydro project in Nigeria
  • Storing Carbon Dioxide Below Ground May Prevent Polluting Above

  • Large-Scale Trial Of HIV Vaccine Launched In South Africa
  • AIDS Vaccine Closer But Remains Elusive
  • Global Vaccine Market To Top 23 Billion Dollars
  • US Overdue For Bird Flu Experts Warn

  • Researchers Unearth 4300-Year-Old Chimpanzee Technology
  • Adaptation To Global Climate Change Is An Essential Response To A Warming Planet
  • Electric Fish Shed Light On Ways The Brain Directs Movement
  • Investigating The Invisible Life In Our Environment

  • Britain Launches Investigation Into Monsanto Toxic Waste
  • Pollution Worsens As Curbs Fail In China
  • Facing Jail US Mining Boss Says Pollution Trial A Sham
  • EU To Propose Laws To Fight 'Green Crimes'

  • Human Ecological Footprint In 2015 And Amazonia Revealed
  • Risk Of Extinction Accelerated Due To Interacting Human Threats
  • Carnegie Mellon Student Develops Mood-Sharing Gadget To Help Computer Users Express Their Feelings
  • Selectivity Is Ultimate Aphrodisiac

  • The content herein, unless otherwise known to be public domain, are Copyright 1995-2006 - SpaceDaily.AFP and UPI Wire Stories are copyright Agence France-Presse and United Press International. ESA PortalReports are copyright European Space Agency. All NASA sourced material is public domain. Additionalcopyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by SpaceDaily on any Web page published or hosted by SpaceDaily. Privacy Statement