In Tibetan Ice, A Chilling History of Global Warming
[WTN-L World Tibet Network News. Published by The Canada Tibet Committee. Issue ID: 00/09/19; September 19, 2000.]
By Tim Friend USA TODAY
The study of ice cores is adding to a growing body of evidence that Earth has heated up over the past century.
The latest findings, reported in the current issue of the journal Science: Ice cores removed from a glacier in the Himalayas suggest that temperatures in southern Asia over the past five decades are the warmest in 1,000 years.
The analysis of cores, taken from an ice field on the flank of a 26,293-foot mountain peak in Tibet, found that temperatures have risen for 50 years and that the past decade was the warmest. The cores also recorded changes in the monsoon cycles over 800 years that resulted in catastrophic droughts in southern Asia.
Ice cores hold a climate record that is as old as the ice field from which they are taken. Ice fields studied in the mountainous regions of Tibet range in age from 40,000 years to 400,000 years. The cores can reveal periods of heavy snowfall or drought, annual temperatures, and many other components of climate, says Lonnie Thompson of Ohio State University, who led the latest research.
Of particular concern from this study and two previous studies by the same team is the shrinking of snow caps or ice fields on some of the world's tallest mountains along the middle latitudes.
For at least the past 10,000 years, these permanent ice fields have been an essential source of water for most of the world's population.
As most schoolchildren learn, snow and ice accumulate in the winter atop mountains, then melt in the spring and summer to provide water for rivers. Those rivers are essential for agriculture and provide drinking water for billions of people.
But as the snow peaks shrink, the amount of water cascading down to the rivers will diminish. Scientists in India have found that situation occurring in the Himalayas.
The Ohio State team has studied ice fields in Peru, the Himalayas and on Africa's Kilimanjaro over the past 25 years.
"The ice fields are losing mass. It's hard to get a handle on whether that is due to a reduction in precipitation or due to warmer temperatures,'' says Ellen Mosley-Thompson, part of the Ohio State research team. "The indications are that it is from warming. The implications are severe for the regions that rely on permanent ice fields for continued flow of water in the rivers. In South America, the ice fields are diminishing, and the same is happening in the Himalayas."
Kilimanjaro has lost about 75% of the mass of its ice field since 1900.
Other research reported recently has found similar reductions in the size of glaciers and in the thickness of ice sheets in the northern polar latitudes. The Antarctic Peninsula also is undergoing a rapid rate of warming.
"Something unusual is happening in the climate history of the 20th century," Mosley-Thompson says." If it is due to human activity, and I happen to believe that is highly probable, I think we are just on the cusp of getting the answers. But the diminishment of water resources is occurring now, and the impact will be felt long before we have the answers to global warming."
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