China has admitted that climate change will have a massive impact on the country, as it faces worsening floods and falling crop production.

Its first report on the subject warns of more serious droughts in farm regions, of worsening floods and of falling crop production but has come up with unambitious targets to prevent such disasters.

Despite the rapid pace of industrialisation, it has even postponed indefinitely a national plan to combat the effects of global warming.

The decision reflects the differences between politicians, anxious that their industrial engine provide jobs for all today, and climate scientists, who worry about pollution and its fallout for future generations.

China is already poised to overtake the United States as the world’s biggest emitter of carbon dioxide - possibly this year and no later than next year, the International Energy Agency said at the weekend.

With China opening one new coal-fired power plant every four days, it has already become a question of when - not if - China will become the world’s largest producer of greenhouse gases.

The National Climate Assessment Report says that China has warmed up more than most countries in the past half century and faces serious consequences. For example, since 1950, the number of frosty days each year has decreased by ten, on average. "By 2020, the average temperature in China will increase 1.1C-2.1C, causing worsening droughts in northern China and extreme weather," the report said.

This will result in increased floods in the east and more droughts in the west. The higher-than-average temperatures will mean spreading deserts, shrinking glaciers and the increased spread of diseases.

By the end of the century, glaciers on the Tibet plateau that feed the mighty Yangtze river - an important source of water and power for the Shanghai basin and its hinterland - could shrink by two-thirds. Intensifying rainfall further downstream would trigger landslides and other geological disasters around the massive Three Gorges Dam across the Yangtze. Water scarcity and extreme weather could reduce nationwide crop production by as much as 10 per cent by 2030. Wheat, rice and corn growing capacity could drop by up to 37 per cent in the second half of the century.

The report says: “If we do not take any actions, climate change will seriously damage China’s long-term grain security.” That is a risk that cuts to the heart of Communist credibility since the party has cited its commitment to ensuring sufficient food - in particular, rice - for all as one of the reasons for its legitimacy since it swept to power in 1949.

It rules out absolute and compulsory caps before 2050 on China''s soaring greenhouse gas emissions in favour of much less ambitious goals. Instead, it suggests cutting the amount of heat-trapping carbon dioxide created per unit of national wealth. That, if adopted, would be China’s first - albeit unambitious - climate change goal.

Using a measure known as carbon intensity, it would reduce emissions of carbon dioxide per unit of gross domestic product by 40 per cent in the period from 2000 to 2020. However, China’s aim over the same two decades is to quadruple its GDP, so that even in reaching its carbon intensity goal it would more than double emissions.

The European Union’s executive commission says that is incompatible with avoiding more dangerous climate change. The commission reckons that, to minimise dangerous warming, greenhouse gas emissions will have to fall in rich nations and no more than double in developing countries from 1990 to 2020.

The Chinese report cuts to the heart of the concerns of the ruling Communist Party to retain its grip on power by ensuring economic prosperity without loosening control. It said that international emission limits were unfair and could cause economic problems, emphasising that the country lacks the technology to meet such ambitious goals. Its leaders are also concerned that shutting older factories or power plants could wipe out jobs in poor areas, where the Government fears unrest among the unemployed.

It said: “If we prematurely assume responsibilities for mandatory cuts in greenhouse gas emissions, the direct consequence will be to constrain China’s current energy and manufacturing industries.”