"If we do not take any measures, by the second half of the 21st century production of key agricultural products like wheat, rice and corn could fall by up to 37 percent," Xinhua quoted the report as saying.

Warmer temperatures could also increase pressure on China's already scarce water resources, change its forestry industry, cause flooding along the coastline and massive melting of glaciers, and extend the range of diseases like malaria.

"These impacts will mostly be negative, and some of them cannot be reversed," the report added.

Earlier excerpts from the report were carried in state media in late December. The full text is expected to be released in the first half of 2007.

It was put together mainly by the Ministry of Science and Technology, the Chinese Meteorological Administration and Chinese Academy of Sciences.

The report is likely to stir debate about whether and how China can balance its ambitious goals for economic growth with steps to rein in rising greenhouse gas emissions from industry and cars, which keep heat in the atmosphere and threaten to dramatically increase the planet's average temperatures.

Extreme weather already costs China up to 6 percent of its national earnings each year, the country's top weather official said late in 2006, but global warming does not appear high on top officials' priority lists.

Beijing is pushing an energy efficiency drive because of worries about growing dependence on imported oil. This could indirectly help reduce emissions of greenhouse gases since over 80 percent of the country's power comes from coal-burning plants.

But top leaders rarely mention rising temperatures and although China has ratified the Kyoto Protocol it has resisted calls for a cap even on emissions growth -- although the International Energy Agency says it could be top emitter by 2009.

Chinese officials argue that most carbon dioxide currently in the atmosphere was produced by developed nations as they industrialised, and they have no right to deny the same economic growth to others.