The increasingly frequent occurrence of extreme weather and unusual climatic events, now seriously endangering human society, is believed to have a close connection with global warming.

More than 150 meteorologists from nearly 40 countries, including China, the United States, Britain and Canada, are looking for a scientific way of studying changes in weather and climate extremes at an international workshop held by the Intergovernmental Panel on Climate Change (IPCC).

Statistics show that five times more major meteorological calamities occurred in the 1990s than in the 1950s. The world's annual economic loss due to these disasters also soared from US$4 billion in the 1960s up to US$29 billion.

Qin Dahe, co-chair of the IPCC Working Group One and director of the China Meteorological Administration (CMA), cited climatic hazards, to great extent, as an aftermath of human activities.

According to Qin, urbanization can lead to heat-island effects, and changes in land use can alter the surface albedo, evaporation and runoff. The huge emission of green house gases has irreversibly led to global warming.

These regional and global changes caused by human activities are likely to change the distribution of extreme weather and climate events in terms of locality, frequency and intensity, said Qin.

Scientific research by IPCC indicates that the rise of green house gases in the atmosphere can raise temperature and accelerate evaporation, which often results in an unbalanced distribution of global rainfall and thus may bring more dry spells and floods.

"In China, the frequent drought in the north and floods in the south over recent years reinforce this conclusion," said Ding Yihui, a CMA climate expert.

According to the IPCC Third Assessment Report, the global average temperature will rise by 1.4 to 5.8 degrees Celsius in the next 10 decades.

The report notes that further aggravation of global warming will lead to a more frequent occurrence of extreme weather and climatic events, thus posing great threat to the sustainable socio-economic development of the world.

Meteorologists also show concern over difficulties in weather and climate extremes research.

David Easterling, an expert with the National Climatic Data Center of the United States, acknowledged that one major problem in examining the climate record for changes and extremes is a lack of accurate and long-term data.

"Various countries and regions use different criteria when recording data, which also add to difficulties," said Easterling.

The workshop is aimed primarily to standardize the parameters used in data collection, Ding Yihui said. "But it will take at least a period of 50 years to get accurate and credible observation data."

Moreover, worldwide cooperation is needed to make a scientific conclusion over the changing trends in weather and climate extremes, Ding said.

(Xinhua News Agency June 14, 2002)