Evidence Of Global Warming Reported To Senate Hearing

Published on March 06, 1992

COLUMBUS, Ohio -- An Ohio State University glaciologist told Congress Feb. 27 that he has found evidence of unprecedented global warming in some remote areas of the planet.

Ice core samples he drilled from ice caps in remote areas of South America, on the Tibetan Plateau of China, and in Kirghizia, in the former Soviet Union, reveal recent and rapid warming in the tropics and subtropics.

These, coupled with an unexpected 160-meter (525 feet) retreat of a glacier at the edge of a Peruvian ice cap over the last decade, suggest that the recent warming has been substantial.

"The evidence is very clear that warming is taking place," explained Lonnie G. Thompson, an associate professor of geological sciences and research scientist at the Byrd Polar Research Center at Ohio State.

He presented his findings before the Senate Committee on Commerce, Science and Technology in Washington. He was one of eight scientists invited to the Senate hearing to discuss the latest techniques for gauging global warming.

Thompson said the conditions of the ice on the Quelccaya ice cap in Peru have deteriorated to the point where, if it was a proposed site for new ice core studies, it would be considered unfit because of the recent warming.

"Ice sheets and ice caps are widely recognized as libraries of atmospheric history from which past climatic and environmental conditions may be extrapolated," he said.

"These sites can provide long term records of El Nino/Southern Oscillation and monsoon variability from the regions where most of the Earth's population is concentrated."

If the current warming trend persists, he said, many of these unique tropical and subtropical archives of climate and environmental history may disappear.

"Consequently, the climatic and environmental records from these regions, which may contain key information for understanding our climate system, will be lost permanently."

Thompson and his colleagues have been monitoring climate effects on the Quelccaya ice cap in Peru since 1974. They recently began similar programs on the Dunde ice cap in China in 1984; on the Gregoriev and It-Tish ice caps near the border between the Peoples' Republic of China and Kirghizia in 1990, and in the far Western Kunlun of China in 1990.

Thompson told the committee that, among other techniques, he looks at the ratio of two isotopes -- oxygen-16 and oxygen-18 -- preserved in the ice cores. The higher the ratio, the warmer the temperatures were when the ice formed from fallen snow. From these, he can extrapolate a history of local temperatures in the region.

The oxygen isotope records from ice cores at these four remote locations show a 1-2 part per mille increase in the oxygen-18 : oxygen-16 ratio -- a definite warming. Also, the temperature at the bottom of a 20-meter (66 foot) deep borehole into the Gregoriev ice cap in Kirghizia was 2.2 degrees Celsius warmer last year than it was 28 years earlier.

Thompson also told the congressional committee that the zone on the Quelccaya ice cap where the ice melts and water percolates downward has risen at least 130 meters (430 feet) since 1976. And the Qori Kalis Glacier at the edge of Quelccaya has been retreating 14 meters (46 feet) annually for the last four years, nearly three times the rate of retreat from 1963 to 1978.

These findings, he said, provide "strong evidence of a recent, widespread warming in the tropics and subtropics." He suggested that these areas experienced at least a 1 degree Celsius warming over the last 50 years.

"Viewed from the long perspective available from the central Asian ice core record, the warming of the last 50 years is unprecedented," Thompson said.

Most current models which predict the possible effects of global warming suggest that the first signs of temperature increases will be detected in interior continental sites far from the mitigating effects of oceans. The ice caps Thompson has studied lie in a zone from 13 degrees South to 42 degrees North latitude and between 15,000 and 22,000 feet in elevation.

These and a few other tropical and subtropical ice caps offer annual resolvable stratigraphic records of climatic and environmental change for areas of the planet where little long-term information exists. However, Thompson warned that "these sensitive archival systems may be lost forever if the current warming trend persists."

Thompson's work has included partnerships with the Lanzhou Institute of Glaciology and Geocryology in China, the former USSR Institute of Geography, Moscow, and Electro-Peru and Servicio Nacional de Meteorologia e Hidrologia, Peru.

At the Senate hearing, he was joined by climate experts from the universities of Utah and Arizona, Princeton University, the Lamont-Doherty Geological Observatory, the National Oceanic and Atmospheric Administration, NASA, and the Navy.

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Contact: Lonnie G. Thompson (614) 292-6531 Written by Earle Holland, (614) 292-8384

EDITOR'S NOTE: Videotape of field studies to ice caps in Peru, China and Kirghizia is available. Color slides showing the retreat of the Qori Kalis Glacier at the edge of Quelccaya ice cap are also available. Requests should be made to Earle Holland at the Office of University Communications, Ohio State University, (614) 292-2711.



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