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

More articles from Earth Sciences:

nachricht Clear as mud: Desiccation cracks help reveal the shape of water on Mars
20.04.2018 | Geological Society of America

nachricht Hurricane Harvey: Dutch-Texan research shows most fatalities occurred outside flood zones
19.04.2018 | European Geosciences Union

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Spider silk key to new bone-fixing composite

University of Connecticut researchers have created a biodegradable composite made of silk fibers that can be used to repair broken load-bearing bones without the complications sometimes presented by other materials.

Repairing major load-bearing bones such as those in the leg can be a long and uncomfortable process.

Im Focus: Writing and deleting magnets with lasers

Study published in the journal ACS Applied Materials & Interfaces is the outcome of an international effort that included teams from Dresden and Berlin in Germany, and the US.

Scientists at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) together with colleagues from the Helmholtz-Zentrum Berlin (HZB) and the University of Virginia...

Im Focus: Gamma-ray flashes from plasma filaments

Novel highly efficient and brilliant gamma-ray source: Based on model calculations, physicists of the Max PIanck Institute for Nuclear Physics in Heidelberg propose a novel method for an efficient high-brilliance gamma-ray source. A giant collimated gamma-ray pulse is generated from the interaction of a dense ultra-relativistic electron beam with a thin solid conductor. Energetic gamma-rays are copiously produced as the electron beam splits into filaments while propagating across the conductor. The resulting gamma-ray energy and flux enable novel experiments in nuclear and fundamental physics.

The typical wavelength of light interacting with an object of the microcosm scales with the size of this object. For atoms, this ranges from visible light to...

Im Focus: Basel researchers succeed in cultivating cartilage from stem cells

Stable joint cartilage can be produced from adult stem cells originating from bone marrow. This is made possible by inducing specific molecular processes occurring during embryonic cartilage formation, as researchers from the University and University Hospital of Basel report in the scientific journal PNAS.

Certain mesenchymal stem/stromal cells from the bone marrow of adults are considered extremely promising for skeletal tissue regeneration. These adult stem...

Im Focus: Like a wedge in a hinge

Researchers lay groundwork to tailor drugs for new targets in cancer therapy

In the fight against cancer, scientists are developing new drugs to hit tumor cells at so far unused weak points. Such a “sore spot” is the protein complex...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

IWOLIA: A conference bringing together German Industrie 4.0 and French Industrie du Futur

09.04.2018 | Event News

 
Latest News

Magnetic nano-imaging on a table top

20.04.2018 | Physics and Astronomy

Start of work for the world's largest electric truck

20.04.2018 | Interdisciplinary Research

Atoms may hum a tune from grand cosmic symphony

20.04.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>