This environmental upheaval could derail the ruling Communist Party's plans for sustainable development, a copy of the report obtained by Reuters says.

"Climatic warming may have serious consequences for our environment of survival as China's economic sectors, such as agriculture and coastal regions, suffer grave negative effects," the report states.

Fast-industrialising China could overtake the United States as the world's top emitter of human-generated greenhouse gases as early as this year, and Beijing faces rising international calls to accept mandatory caps on carbon dioxide emissions from factories, fields and vehicles.

But underscoring China's commitment to achieving prosperity even as it braces for climate change, the report rejects emissions limits as unfair and economically dangerous, citing what it says are uncertainties about global warming.

"If we prematurely assume responsibilities for mandatory greenhouse gas emissions reductions, the direct consequence will be to constrain China's current energy and manufacturing industries and weaken the competitiveness of Chinese products in international and even domestic markets," it says.

The 400-page report was written over several years by experts and officials from dozens of ministries and agencies, representing China's first official response to global warming.

With its mixture of dire warnings and caveats, it bears the markings of bureaucratic bargaining.

China was one of a few countries that challenged claims about global warming presented in a draft report at a UN climate change meeting in Brussels earlier this month. That report was approved after some claims were softened and passages removed.

China's own national report says "uncertainties over climate change issues" justify rejecting international limits on greenhouse gas emissions.

DISASTERS

But other parts of the report assert that the country's brittle environment will be severely tested by climate change.

By the end of the century, glaciers on the Qinghai-Tibet highlands that feed the Yangtze river could shrink by two thirds. Further downstream, increasingly intense rainfall could "spark mud and landslides and other geological disasters" around the massive Three Gorges Dam.

Coastal cities will need to build or strengthen barriers to ward off rising sea levels.

Unless steps are taken, water scarcity and increasingly extreme weather could reduce nationwide crop production by up to 10 percent by 2030. Wheat, rice and corn growing capacity could fall by up to 37 percent in the second half of the century.

"If we do not take any actions, climate change will seriously damage China's long-term grain security," the report states.

China has repeatedly ruled out accepting mandatory international emissions limits, saying that rich countries are responsible for the accumulation of greenhouse gases and should not look to poorer countries for a way out.