Chinese scientists say global warming caused by ozone-depleting gases will 'substantially improve' mainland grain harvests, even though coastal cities such as Hong Kong and Shanghai may be swallowed by rising seas. 'The warm climate will greatly strengthen the effects of the wind coming off the ocean further inland,' scientists from the Chinese Academy of Meteorological Science have concluded in an essay in the official periodical Beijing Review. 'Rainfall brought by the summer wind will substantially improve the environment in drought areas,' they said. More than a quarter of China's territory is drought-stricken or eroded by desert, by official estimate. 'The warming climate can bring benefits to China and many developing countries,' scientists said. State planners have vowed China must achieve self-sufficiency in food production in the next century, when the mainland's population is forecast to peak at 1.6 billion people. Ren Zhenqiu, a senior academy scientist, predicted 21st century global warming would mark an 'economically and culturally prosperous period' for China while devastating the United States' farm economy. China's emissions of ozone-depleting substances have doubled over the past decade, according to federal environmental surveys. 'Can the prosperity brought by the warm period compensate for the loss of submerged economically developed coastal areas? That is a question I cannot answer,' Mr Ren said. Scientists have theorised that global warming will melt the polar ice caps, leading to dangerously high sea levels that may threaten coastal areas.