Water shortages in China are reaching "incredible" proportions, a British environmental expert said on Monday night, citing Shanghai as a particularly vulnerable location unless dramatic action is taken quickly.

"The Chinese are facing an incredible water-stressed economy," Justin Mundy, a government adviser on climate change said during a presentation on the potentially dire consequences of unchecked global warming.

He pointed to the current low levels of aquifers in Shanghai as a prime example of the problems China faces.

Shanghai is going to have to use desalinized water in the next 10 years, then build the infrastructure to import water from Southwest China, he said.

"All the water in Southwest China is fed by glacial melt," he said. "Glacial melt in about 25 years' time is not going to be there in anything like the capacity that is going to be required. What then, Shanghai?"

And Shanghai is not alone, Mundy said, contending that 21 of the world's 33 largest cities -- those with populations of 8 million or more face eventual water supply crises.

Mundy's presentation drew from a newly released report by economist Sir Nicholas Stern that estimates that global warming could shrink the world economy by 20 percent over time, but said the costs will be far less if concerted action is taken now.

Mundy said nations must begin by cooperating with one another, scrapping traditional concepts of seeking national advantage in international exchanges.

"Up to now, foreign policy, geopolitics, has to some extent been a game of chess, seeking advantage with one piece or the other," Mundy said. "Our problem is, it is not the game of chess that is now at stake. What is now at risk is the chess board itself."

The Stern Report highlighted the risk of serious, irreversible impact of climate change as concentrations of greenhouse gases rise.

It said a temperature increase in the range of 5 degrees centigrade would over time cause a sea level rise enough to threaten London, Shanghai, New York, Tokyo and Hong Kong.

Source: China Daily/Agencies