Monsoon Likely to Return to World Roof: Experts

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Last updated at: (Beijing Time) Wednesday, April 10, 2002

Monsoon Likely to Return to World Roof: Experts

Thanks to global warming, monsoon rains are likely to return to the "Roof of the World", the Qinghai-Tibet Plateau, after an absence of 30,000 years. Experts believe that 30,000 to 40,000 years ago, the rainfall on the plateau was about 40 to 100 percent greater than today.

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Thanks to global warming, monsoon rains are likely to return to the "Roof of the World", the Qinghai-Tibet Plateau, after an absence of 30,000 years.

Temperatures approaching that of the interglacial era

Shi Yafeng, an academician with the Chinese Academy of Sciences,told Xinhua that rising temperatures are increasingly approaching that of the interglacial era, dating back 30,000 to 40,000 years, when the weather was warm and humid throughout the area of today'sChina.

China's western region was then dotted with lakes and rivers aswell as abundant tree growth, Shi said.

According to authoritative statistics, if the carbon dioxide content in the atmosphere keeps rising at the current speed, by 2050 the temperature will be an average 2.2 degrees Celsius higheracross the country than today, and the temperature on the Qinghai-Tibet Plateau may rise by 2.6 degrees.

Ice core samples from the western part of Kunlun Mountains showthe plateau's temperature during the interglacial age was four degrees higher than at present. Analysis of the lakebed deposits of Qaidam Lake shows that the temperature then was two degrees higher.

Experts believe that 30,000 to 40,000 years ago, the rainfall on the plateau was about 40 to 100 percent greater than today.

The study shows that in the interglacial age, the area of lakesin the Qaidam Basin was 25,000 square kilometers and the water surface was 50 to 60 meters higher than the present level. A patchof salt marsh now, Baijian Lake in Minqin County, Gansu Province, was once as large as 16,000 square kilometers.

A study of the sporopollen stratum of the Yabrai Mountain also indicates various broad-leaved trees flourished in the western areas 30,000 to 40,000 years ago.

Shi explained, "During that period, the southwest monsoons wereso powerful that they carried abundant vapor from the Indian Oceanand the Southern Hemisphere areas to cross over the Himalayas and the Qinghai-Tibet Plateau, where altitudes were similar to the present." ��

According to the academician, the changes in solar radiation, which were caused by astronomic factors in the interglacial age, produced great heat, resulting in a remarkable increase in the difference in temperatures between the land and the sea.

This consequently intensified monsoon activities and low pressure on the Qinghai-Tibet plateau in the summer, and the monsoon vapor was thus drawn across the Himalayas and fell on the plateau, Shi said.

Global warming caused by the carbon dioxide increases might lead to the same result, Shi said.

Statistics by the United Nations show that the content of the gas, the main cause of the so-called "greenhouse effect", is at its densest for hundreds of thousands of years.

Impacts of inevitable global warming

Ding Yihui, a climate expert with the China Meteorological Administration (CMA), said that despite the signing of the Kyoto Protocol on reducing discharges of carbon dioxide, the "greenhouse" gas will continue to increase this century. Generally, the global warming is inevitable and the southwest monsoon will get stronger.

"The warm and humid airflows brought by the strong monsoons will probably reverse desertification in the western region and promote biological diversity," he said.

However, he also warned of the negative impacts of climate warming as well as the thawing of ice and snow.

Deserts in the Gobi and high mountains, with an annual precipitation of less than 200 mm, occupy almost half of China's western region. The western region takes up 56 percent of the country's territory.

Ding also pointed out that sulfide aerosol emitted by coal burning has a cooling function to markedly offset the greenhouse effect of the carbon dioxide. As a result, the southwest monsoon hasn't shown the signs of increasing intensity yet.

However, he said that due to the greater international control over sulfide, the sulfide content in the atmosphere will keep decreasing this century.

Shi attributed the formation of climate changes to many factors,but it still needs more simulation experiments and deeper climaticstudies to foretell accurately whether the old climate pattern will return in the future.

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