The warming weather may pose a challenge to the China's long-term food security, according to an official report on climate change.

China's output of major crops like 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 the country's water supplies. Some damage will be irreversible, says the report.

The average temperature in China has risen by 0.5 to 0.8 degrees in the past century and is expected to go up another 2 to 3 degrees in the coming 50 to 80 years, the report says. 

Most parts of China, especially northern areas, will become drier even though annual rainfall may increase 7 to 10 percent, it said. The greater demand for water for agriculture will affect the price of farm produce, the report indicates. 

Last year Chongqing Municipality and neighboring province Sichuan in southwest China were hit hard 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 states. It also predicted that floods and droughts would be more common as water evaporated more rapidly from rivers.

The rate of evaporation of water from the Yellow River, China's second longest waterway, will increase by 15 percent a year, says the report. It also warns that coastal areas would face a greater threat of flooding since the sea level around the country is expected to increase by 1 to 16 centimeters by 2030.

The Chinese government will have to achieve 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 released by six central departments and academic organizations.

(Xinhua News Agency January 4, 2007)