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Summer 1997

Science Bits

University of Illinois at Urbana-Champaign
Changing climate may hurt less developed countries, help developed ones

A recent modeling study shows that global climate change is likely to have greatly disparate impacts on the developed and the less developed nations of the world. The model predicts that "developed countries--the primary emitters of carbon dioxide--would benefit by $82 billion per year, while underdeveloped countries would suffer by $40 billion per year," according to Michael Schlesinger (University of Illinois at Urbana-Champaign).

Schlesinger worked with colleagues Natalia Andronova (University of Illinois), Robert Mendelsohn (Yale University), and Wendy Morrison (Middlebury College). In March, Schlesinger presented their results in a paper titled "Country-Specific Market Impacts of Climate Change" at the Intergovernmental Panel on Climate Change Asia-Pacific Workshop on Integrated Assessment Models, held at the United Nations University, Tokyo, Japan.

The researchers used two versions of a University of Illinois general circulation model, running on NCAR's supercomputers, to simulate a 2-degree-C increase in global mean temperature as a result of doubled atmospheric concentrations of carbon dioxide. They expect these conditions to prevail by about the year 2060.

The researchers used the models' geographic distribution of temperature and precipitation changes to determine specific annual changes in these factors for 184 countries. In addition to these national data, they used economic data on agriculture, forestry, coastal resources, energy, and tourism to calculate market impacts of the potential changes.

If the model results prove accurate, "clearly, some countries will be big winners and others will be large losers," Schlesinger said. "For example, Canada, the former Soviet Union, and the United States would receive annual benefits of $31 billion, $39 billion, and $22 billion, respectively, while Brazil, India, and Mexico would lose $14 billion, $22 billion, and $8 billion per year, respectively."

The countries that would suffer the most from global warming are island nations, according to Schlesinger. "These countries have long coast lines, sensitive tourism industries, and small, undeveloped economies." Of the continents, Europe and North America would benefit, while the others, including Australia, would fare poorly. "But there are important exceptions among countries within continents," said Schlesinger. "For example, although Asia would lose from global warming, China would gain. And, although, Europe and North America would gain from global warming, Spain, Portugal, and Mexico would all suffer."

The modeled results offer a useful measure of potential impacts by countries, but Schlesinger pointed out, "Natural variability in the climate system may be of more importance to certain impacts than the changes in the average temperature and precipitation. In agriculture, for example, the frequency of frosts, droughts, or severe thunderstorms has a tremendous impact that is not yet captured in our analysis. Also, the nonmarket impacts may turn out to be more important than the market impacts. So this is not the end of the story."


University of Colorado at Boulder
Active volcanoes on Venus?

Recent observations by Larry Esposito (University of Colorado at Boulder) using the Hubble Space Telescope have shown that sulfur dioxide (SO2) values at cloud-top level on Venus have declined by a factor of five since the Pioneer Venus satellite observations ended in the fall of 1992. The decline, which continues a trend observed throughout the 1980s, suggests that a massive volcanic eruption in the early 1970s may have colored researchers' beliefs about the Venerian atmosphere for the last 20 years.

Esposito reported his results at a NASA space astronomy teleconference in February. He calls Venus "the Earth's evil twin." It has a dense carbon dioxide atmosphere and surface temperatures of 400 degrees C (750 degrees F). With a permanent cover of sulfuric acid clouds, it has both a runaway greenhouse effect and acid rain.

In the early 1970s, SO2 levels on Venus were believed to be fairly low--only tens of parts per billion. The gas was first detected in the atmosphere of Venus in 1978 by Earth-based observations, a fact Esposito believes indicates that its abundance had become at least an order of magnitude greater than previously thought. Continuous observations by the Pioneer Venus satellite from 1978 to 1992 showed that the cloud-top levels of SO2 were steadily declining. Scientists understood where the SO2 was going: it leaves the atmosphere when it is broken apart by sunlight and the sulfur is rained out--just as on Earth, SO2 emitted by coal-fired power plants is washed out of the atmosphere in acid rain. But they were not sure how it got there in the first place.

Some scientists, including Esposito, theorized that this situation was created by an immense volcanic eruption right before the arrival of Pioneer Venus. When the Magellan orbiter mapped Venus's surface by radar in 1991, it found many features that could be volcanic in origin, although no clear-cut evidence that any were active.

Using the Goddard High Resolution Spectrograph instrument on the Hubble, Esposito obtained the best spectral resolution of Venus ever made from a spacecraft. The observations are in the ultraviolet region of the electromagnetic spectrum, where cloud patterns become distinctive. The instrument recorded SO2 values of 10-25 parts per billion, which is consistent with what scientists believed to be the values before the late 1970s. "A natural conclusion [of the new results] is that Venus has again achieved a chemical and dynamic state that was disrupted by injection of SO2 in the 1970s," says Esposito.

Hubble observations of Mars have shown a similar disparity between the climate that researchers inferred from visits by unmanned Viking spacecraft in the mid-1970s and the Martian climate of today, which is cooler and drier. These findings indicate that the atmospheres of Earth, Mars, and Venus have at least one thing in common: they can only be understood through long-term monitoring.


Ohio State University
Tropical clues to global warming

A team of Ohio State University researchers suggests that some of the most compelling evidence for recent global warming may be found in the tropics and subtropics, rather than in the polar regions, where early signs of warming have been anticipated.

Ice caps in alpine regions throughout the tropics and subtropics are melting at a phenomenal rate, according to Ellen Mosley-Thompson and Lonnie Thompson, both researchers at the Byrd Polar Research Center at OSU. They reported their findings at a meeting of the Association of American Geographers in April.

The scientists cited the following changes:

"Most of the evidence for warming that we see in these high alpine ice caps is in regions that are already water-stressed," Mosley-Thompson said. "These tropical areas are where most of the planet's population lives and where subsistence agriculture is incapable of feeding the population. And in the future, the greatest increase in population will occur here."


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