Rising temperatures may pose a challenge to the long-term food security of China, the world's most populous country, according to an official report evaluating climate change.

China's output of major crops, including rice, wheat and corn, could fall by up to 37 percent in the second half of this century if no effective measures are taken to curb greenhouse gases in the coming 20 to 50 years, according to the report.

Global warming will negatively impact China's ecological, social and economic systems, especially farming, animal husbandry and water supply, and some damage will be irreversible, said the report.

The average temperature in China has risen by 0.5 to 0.8 degree centigrade in the past century and is expected to go up another two to three degrees centigrade in the coming 50 to 80 years, it said.

Most areas in China, especially northern areas, will get drier, even though annual rainfall may increase 7 to 10 percent, it said.

The greater demand for water for agriculture will impact the cost of farm produce, it reasoned.

This year, China's southwestern Chongqing Municipality and neighbouring province Sichuan were ravaged by the worst drought in more than 50 years.

China's central and western regions will suffer an annual water shortage of about 20 billion cubic meters from 2010 to 2030, the report said.

The report also predicted that more floods and droughts will hit the country as water evaporates more rapidly from rivers.

The Yellow River, China's second longest, will see evaporation increase by 15 percent a year, it said.

It also warned that coastal areas will be at a greater risk of flooding as China's sea level will climb 1 to 16 centimeters by 2030.

The Chinese government will strive to realize zero or even negative growth of carbon dioxide emissions by the middle of this century, according to the report.

It outlined China's overall plan for dealing with climate change.

"China will reduce carbon dioxide emissions by moving away from a labor-intensive economy towards a technology-driven economy, making better use of energy resources, protecting the environment and developing advanced nuclear energy and other renewable energies," it said.

In 2002, China's carbon dioxide emissions totaled 4.08 billion tons, the second highest in the world after the United States.

The report was jointly released by six central departments and academic organizations, including the Ministry of Science and Technology, China Meteorological Administration and the Chinese Academy of Sciences.

Source: Xinhua