Subscribe to our free daily newsletters
. Earth Science News .

Subscribe to our free daily newsletters

Flooding risk from global warming badly under-estimated: study

by Staff Writers
Paris (AFP) Aug 29, 2007
Global warming may carry a higher risk of flooding than previously thought, according to a study released on Wednesday by the British science journal Nature.

It says efforts to calculate flooding risk from climate change do not take into account the effect that carbon dioxide (CO2) -- the principal greenhouse gas -- has on vegetation.

Plants suck water out of the ground and "breathe" out the excess through tiny pores, called stomata, in their leaves.

Stomata are highly sensitive to CO2. The higher the level of atmospheric CO2, the more the pores tighten up or open for shorter periods.

As a result, less water passes through the plant and into the air in the form of evaporation. And, in turn, this means that more water stays on the land, eventually running off into rivers when the soil becomes saturated.

In a paper published in February 2006, British scientists said the CO2-stomata link explained a long-standing anomaly.

Over the last 100 years the flow of the world's big continental rivers has increased by around four percent, even though global temperatures rose by some 0.8 degrees Celsius (1.35 degrees Fahrenheit) during this period.

Today, as a result of the unbridled burning of oil, gas and coal, levels of CO2 in the atmosphere are around a third more than in pre-industrial times in the middle of the 18th century.

The new study takes the 2006 discovery an important step further by projecting what could happen to water runoff in the future.

If CO2 levels double compared with pre-industrial concentrations -- a common scenario in climate simulations -- the effect on plants alone would lead to an increase of six percent in global runoff, it says.

Until now, scientists have generally estimated an increase in runoff of between five and 17 percent compared with the pre-industrial era.

But this is based only on one yardstick, called radiative forcing. In other words, it only measures the warming effect that greenhouse gases have on the water cycle and not the indirect impact that CO2, the biggest culprit, has on vegetation.

The "radiative forcing" yardstick also predicts that higher temperatures will increase evaporation, causing greater water stress and longer droughts.

Both forecasts are offbeam, says the new paper.

By widening the picture to include the CO2-stomata factor, the likelihood is that the risk of flooding will be worse than thought, but the risk of drought rather less so.

"The risks of rain and river flooding may increase more than has been previously anticipated, because intense precipitation events would be more likely to occur over saturated ground," it says.

"In contrast, the risks of hydrological drought may not increase as much as expected on the basis of meteorological changes alone."

Flooding is a major problem, especially in poor countries that do not have the money to upgrade drainage systems to cope with runoff from saturated soils.

Since June, nearly 3,200 people in South Asia have been killed by heavy monsoon rains and snow melt. More than 20 million people have been affected in the eastern Indian state of Bihar alone.

The authors of the Nature paper are led by Richard Betts of the Hadley Centre for Climate Prediction and Research, part of Britain's Met Office.

Email This Article
Comment On This Article

Related Links
Climate Science News - Modeling, Mitigation Adaptation

Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News

Greenhouse Gases Likely Drove Near-Record US Warmth In 2006
Washington DC (SPX) Aug 29, 2007
Greenhouse gases likely accounted for over half of the widespread warmth across the continental United States in 2006, according to a new study that will be published 5 September in Geophysical Research Letters, a publication of the American Geophysical Union. Last year's average temperature was the second highest since recordkeeping began in 1895. The team found that it was very unlikely that the 2006 El Nino played any role, though other natural factors likely contributed to the near-record warmth.

  • NKorea searches for fugitives after floods: aid group
  • Devastated New Orleans mourns Katrina dead two years on
  • Ground-Breaking Antilandmine Radar
  • Wave of refugees quits Peru quake ruins

  • Flooding risk from global warming badly under-estimated: study
  • Greenhouse Gases Likely Drove Near-Record US Warmth In 2006
  • Climate Change Goes Underground
  • Corals And Climate Change

  • European Hot Spots And Fires Identified From Space
  • China Develops Beidou Satellite Monitoring System
  • DigitalGlobe Announces Launch Date For WorldView-1
  • Radar reveals vast medieval Cambodian city: study

  • US casts doubt on global carbon market
  • Mohawk Chosen To Help Primetime Emmy Awards Reduce Carbon Footprint
  • Oil Imports And Oil Prices Drive US To Increase Renewable Energy Capacity
  • Enerize And FiFe Batteries Partner Up On Li-Ion Batteries For HEV Applications

  • Discovery May Help Defang Viruses
  • China probably 'covered up' pig disease outbreaks
  • Online gamers rehearse real-world epidemics
  • Nanoparticle Could Help Detect Many Diseases Early

  • Social Parasites Of The Smaller Kind
  • The World's Oldest Bacteria
  • New Continent And Species Discovered In Atlantic Study
  • Giant Panda Could Survive As An Evolutionary Development

  • Innovative Civil Engineering Application Promises Cleaner Waters
  • Toxic Air Pollution In Urban Parking Garages Study Finds SUVs Bigger Polluters
  • e-Science Points To Pollution Solutions
  • Team Tracks Antibiotic Resistance From Swine Farms To Groundwater

  • Not All Risk Is Created Equal
  • Area Responsible For Self-Control Found In The Human Brain
  • Milestone In The Regeneration Of Brain Cells: Supportive Cells Generate New Nerve Cells
  • Gene Regulation, Not Just Genes, Is What Sets Humans Apart

  • The content herein, unless otherwise known to be public domain, are Copyright 1995-2007 - SpaceDaily.AFP and UPI Wire Stories are copyright Agence France-Presse and United Press International. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights 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