Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Scientists find climate change is major factor in drought’s growing reach

12.01.2005


The percentage of Earth’s land area stricken by serious drought more than doubled from the 1970s to the early 2000s, according to a new analysis by scientists at the National Center for Atmospheric Research (NCAR) in Boulder, Colo. Widespread drying occurred over much of Europe and Asia, Canada, western and southern Africa, and eastern Australia. Rising global temperatures appear to be a major factor, says NCAR scientist Aiguo Dai.



Dai will present the new findings on Weds., Jan. 12th at the American Meteorological Society (AMS) annual meeting in San Diego, Calif. The work also appeared in a paper published in the December issue of the Journal of Hydrometeorology; co-authors are NCAR’s Kevin Trenberth and Taotao Qian.

The study was supported by the National Science Foundation (NSF), NCAR’s primary sponsor. "The results reconfirm the complexity of the climate system," says Cliff Jacobs, program director in NSF’s division of atmospheric sciences. "We need to continue to develop a wide variety of research tools to understand these changes."


Dai and colleagues found that the fraction of global land experiencing very dry conditions rose from about 10-15 percent in the early 1970s to about 30 percent by 2002. Almost half of that change is due to rising temperatures rather than decreases in rainfall or snowfall, according to Dai. "These results point to increased risk of droughts as human activity contributes to global warming," says Dai.

Even as drought has expanded across Earth’s land areas, the amount of water vapor in the air has increased over the past few decades. Average global precipitation has also risen slightly. However, as Dai notes, "surface air temperatures over global land areas have increased sharply since the 1970s." The large warming increases the tendency for moisture to evaporate from land areas. Together, the overall area experiencing either very dry or very wet conditions could occupy a greater fraction of Earth’s land areas in a warmer world, Dai says. "Droughts and floods are extreme climate events that are likely to change more rapidly than the average climate," says Dai. "Because they are among the world’s costliest natural disasters and affect a very large number of people each year, it is important to monitor them and perhaps predict their variability."

To see how soil moisture has evolved over the last few decades, Dai and colleagues produced a unique global-scale analysis using the Palmer Drought Severity Index, which for decades has been the most widely used yardstick of U.S. drought. The index is a measure of near-surface moisture conditions and is correlated with soil moisture content.

Since the Palmer index is not routinely calculated in most of the world, Dai and colleagues used long-term records of temperature and precipitation from a variety of sources to derive the index for the period 1870–2002. The results were consistent with those from a historical simulation of global land surface conditions, produced by a comprehensive computer model developed by scientists at NCAR, NASA, Georgia University of Technology, the University of Texas at Austin, and the University of Arizona.

By factoring out rainfall and snowfall, Dai and colleagues estimated how much of the global trend in soil moisture was due solely to rising temperatures through the extra evaporation they produce. "The warming-induced drying has occurred over most land areas since the 1970s," says Dai, "with the largest effects in northern mid- and high latitudes." In contrast, rainfall deficits alone were the main factor behind expansion of dry soils in Africa’s Sahel and East Asia. These are regions where El Niño, a more frequent visitor since the 1970s, tends to inhibit precipitation.

Though most of the Northern Hemisphere has shown a drying trend in recent decades, the United States has bucked that trend, becoming wetter overall during the past 50 years, says Dai. The trend is especially notable between the Rocky Mountains and Mississippi River. Other parts of the world showing a moistening trend include Argentina and parts of western Australia. These trends are related more to increased precipitation than to temperature, says Dai. "Global climate models predict increased drying over most land areas during their warm season, as carbon dioxide and other greenhouse gases increase," says Dai. "Our analyses suggest that this drying may have already begun."

At the AMS conference, Trenberth will also present results on Tues., Jan. 11th from a workshop on drought. Among the questions addressed: What is the full range of past drought variability, as revealed by paleoclimate data? What role might droughts associated with abrupt climate change play? Are droughts likely to become more frequent, longer, or more extensive as we move into a future with global warming?

Cheryl Dybas | EurekAlert!
Further information:
http://www.nsf.gov

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: In best circles: First integrated circuit from self-assembled polymer

For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.

In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...

Im Focus: Demonstration of a single molecule piezoelectric effect

Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale

Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...

Im Focus: Hybrid optics bring color imaging using ultrathin metalenses into focus

For photographers and scientists, lenses are lifesavers. They reflect and refract light, making possible the imaging systems that drive discovery through the microscope and preserve history through cameras.

But today's glass-based lenses are bulky and resist miniaturization. Next-generation technologies, such as ultrathin cameras or tiny microscopes, require...

Im Focus: Stem cell divisions in the adult brain seen for the first time

Scientists from the University of Zurich have succeeded for the first time in tracking individual stem cells and their neuronal progeny over months within the intact adult brain. This study sheds light on how new neurons are produced throughout life.

The generation of new nerve cells was once thought to taper off at the end of embryonic development. However, recent research has shown that the adult brain...

Im Focus: Interference as a new method for cooling quantum devices

Theoretical physicists propose to use negative interference to control heat flow in quantum devices. Study published in Physical Review Letters

Quantum computer parts are sensitive and need to be cooled to very low temperatures. Their tiny size makes them particularly susceptible to a temperature...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on High Temperature Shape Memory Alloys (HTSMAs)

15.02.2018 | Event News

Aachen DC Grid Summit 2018

13.02.2018 | Event News

How Global Climate Policy Can Learn from the Energy Transition

12.02.2018 | Event News

 
Latest News

Helping in spite of risk: Ants perform risk-averse sanitary care of infectious nest mates

21.02.2018 | Life Sciences

Fraunhofer ISE Supports Market Development of Solar Thermal Power Plants in the MENA Region

21.02.2018 | Power and Electrical Engineering

A variety of designs for OLED lighting in one easy kit

21.02.2018 | Trade Fair News

VideoLinks
Science & Research
Overview of more VideoLinks >>>