LANZHOU, June 19 -- New data may reinforce the relationship between melting permafrost and global warming.

Permafrost, soil or rock that remains frozen all year round, releases greenhouse gases when it thaws, accelerating global warming, according to Zhang Tingjun, dean of the college of earth and environmental sciences, Lanzhou University in northwest China's Gansu Province.

Zhang has been studying permafrost for many years. With carbon in the atmosphere estimated at about 750 billion tonnes, carbon held in permafrost worldwide exceeds 1.83 trillion tonnes. Climate change which causes permafrost to melt and release greenhouse gases will, in turn, aggravate global warming.

"The effect of carbon stored in permafrost on global warming, if fully released, would probably be larger than the combined influence of all human activities," Zhang said.

Zhang's latest research shows that the Tibetan Plateau accounts for 6 percent of permafrost in the northern hemisphere, and holds 160 billion tonnes of carbon, about 9 percent of the total for the hemisphere.

According to a report published by the institute of Tibetan Plateau research in August, the plateau was warmer in the past five decades than any period in the past 2,000 years, and it will get hotter and more humid in decades to come.

Compared with the permafrost found at high latitudes such as Alaska and Siberia, permafrost in China is more sensitive to climate change. "A temperature rise of one or two degrees Celsius has a limited impact on high-latitude permafrost as it is mostly at eight below zero. Permafrost on the Tibetan Plateau is warmer, less than two below zero most of the time, which means a temperature rise of one degree or two will entail severe degeneration," Zhang said.

Zhang's latest research predicts that permafrost coverage on the plateau will continue to shrink and desertification will get worse, which increases the risks of disasters, including landslides and floods.