Plant Growth Surges 1-3 Years After Global Temperature Spikes, Ncar Scientists Report

October 31, 1997

BOULDER-Although El Nino events or volcanic eruptions can boost or depress global temperatures within months, their strongest impacts on the earth's biosphere may not occur until one to three years later, according to a paper in the October 31 issue of Science. Also, regional analyses show that a global warm spell's initial boost in plant activity is clustered in polar and temperate areas, while heat-stressed tropical and semiarid regions may show an initial drop in plant production. The results lend credence to the notion that biological effects of global change could vary substantially across the globe.

"The Response of Global Terrestrial Ecosystems to Interannual Temperature Variability" was written by B.H. (Rob) Braswell, Ernst Linder, and Berrien Moore, all of the University of New Hampshire (UNH); and David Schimel, National Center for Atmospheric Research (NCAR) in Boulder. According to Schimel, the results highlight the power of new data sets on global change, as well as the usefulness of computer models that connect the atmosphere and biosphere. "We were looking specifically for delayed ecosystem responses in this study because they had been predicted by the models," Schimel notes.

Braswell conducted much of the analysis during a graduate fellowship in global change at NCAR sponsored by Oak Ridge Associated Universities and the University Corporation for Atmospheric Research (UCAR) Climate System Modeling Project. NCAR is operated by UCAR under sponsorship of the National Science Foundation.

The authors used three main sources of data for the period 1979- 94, each compiled and distributed with support from the U.S. Global Change Research Program:

--temperatures derived by satellite for the atmosphere's lowest few kilometers by a National Aeronautics and Space Administration (NASA) microwave sounding unit

--a vegetation index calculated with input from a space-based NOAA radiometer (radiation sensor)

--atmospheric carbon dioxide records collected at the South Pole and at Mauna Loa, Hawaii, by the National Oceanic and Atmospheric Administration (NOAA). Because carbon dioxide is well mixed globally on long time scales, these sites provide a good measure of year-to-year variability.

The global temperature record revealed several multiyear patterns, including warming associated with El Nino events in the 1980s. These patterns were correlated globally with CO2 levels and regionally with vegetation growth. Global carbon dioxide levels, which are steadily rising due to human activities, tended to rise more quickly over the first few months after a global temperature peak. The carbon dioxide levels then rose at a slower pace during the one-to-three-year period after the temperature peak, followed by a gradual reacceleration.

The authors studied the temperature-vegetation relationship by region at data points separated by one degree latitude and longitude (roughly 85 by 110 kilometers, or 50 by 70 miles, at midlatitudes). At the peak of a warm period, plant growth tended to increase in polar and temperate regions and decrease at lower latitudes, including tropical rain forests and drier savanna/grassland regimes. "This contrast suggests that . . . temperature may have direct negative impacts on plant growth or may increase water stress in semiarid ecosystems," the authors note.

However, in the one-to-three-year period after a temperature peak, the patterns appear to reverse: plant growth is enhanced in the warmer and drier regions and limited at higher latitudes. Thus, low-latitude plant growth appears to be driving the enhanced uptake of carbon dioxide during this period.

The paper highlights the importance of regional analyses of climate change to detect areas where effects may run counter to a global average. "This is the first data-based study to consider regionally specific ecosystem responses on a global scale," says Schimel. "The results show quantitatively that ecosystems are sensitive to temperature perturbations."

Writer: Bob Henson

Find this press release on the World Wide Web at http://www.ucar.edu/ucargen/press/contents.html

To receive UCAR and NCAR press releases by e-mail, telephone 303-497-8601 or e-mail butterwo@ucar.edu




National Center for Atmospheric Research/University Corporation for Atmospheric Research

Related Volcanic Eruptions Articles from Brightsurf:

New drone technology improves ability to forecast volcanic eruptions
Specially-adapted drones developed by a UCL-led international team have been gathering data from never-before-explored volcanoes that will enable local communities to better forecast future eruptions.

Volcanic eruptions may explain Denmark's giant mystery crystals
Researchers have long been stumped for an explanation of how tens of millions of years-old giant crystals known as glendonites came to be on the Danish islands of Fur and Mors.

The testimony of trees: How volcanic eruptions shaped 2000 years of world history
Researchers have shown that over the past two thousand years, volcanoes have played a larger role in natural temperature variability than previously thought, and their climatic effects may have contributed to past societal and economic change.

Indian monsoon can be predicted better after volcanic eruptions
Large volcanic eruptions can help to forecast the monsoon over India - the seasonal rainfall that is key for the country's agriculture and thus for feeding one billion people.

Volcanic eruptions reduce global rainfall
POSTECH Professor Seung-Ki Min's joint research team identifies the mechanism behind the reduction in precipitation after volcanic eruptions.

A new tool to predict volcanic eruptions
Earth's atmosphere is made up of 78% nitrogen and 21% oxygen, a mixture that is unique in the solar system.

Oral traditions and volcanic eruptions in Australia
In Australia, the onset of human occupation (about 65,000 years?) and dispersion across the continent are the subjects of intense debate and are critical to understanding global human migration routes.

'Crystal clocks' used to time magma storage before volcanic eruptions
The molten rock that feeds volcanoes can be stored in the Earth's crust for as long as a thousand years, a result which may help with volcanic hazard management and better forecasting of when eruptions might occur.

Super volcanic eruptions interrupt ozone recovery
Strong volcanic eruptions, especially when a super volcano erupts, will have a strong impact on ozone, and might interrupt the ozone recovery processes.

Rare volcanic rocks lift lid on dangers of little-studied eruptions
Unusual rocks discovered on a remote mountainside have alerted scientists to the dangers posed by a little-studied type of volcano.

Read More: Volcanic Eruptions News and Volcanic Eruptions Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.