What problems does global warming cause

Global warming in Hong Kong and China
Global warming could cause drought and possibly famine in China, the source of much of Hong Kong's food, by 2050, a new report predicts. Hong Kong could also be at risk from flooding as sea levels rose. The report recommends building sea-walls around low-lying areas such as the new port and airport reclamations. Published by the World Wide Fund for Nature (WWF), the report, which includes work by members of the Chinese Academy of Meteorological Sciences, uses the most recent projections on climate change to point to a gloomy outlook for China.
By 2050 about 30 to 40 per cent of the country will experience changes in the type of vegetation it supports, with tropical and sub-tropical forest conditions shifting northward and hot desert conditions rising in the west where currently the desert is temperate. Crop-growing areas will expand but any benefit is expected to be negated by increased evaporation of moisture, making it too dry to grow crops such as rice. The growing season also is expected to alter, becoming shorter in southern and central China, the mainland's breadbasket. The rapid changes make it unlikely that plants could adapt.
"China will produce smaller crops. In the central and northern areas, and the southern part, there will be decreased production because of water limitations," Dr. Rik Leemans, one of the authors of the report, said during a brief visit to the territory yesterday. Famine could result because of the demands of feeding the population - particularly if it grows - and the diminished productivity of the land. "It looks very difficult for the world as a whole" he said.
Global warming is caused by the burning of large amounts of fossil fuels, such as coal and oil, which release gases that trap heat in the atmosphere. World temperatures already have increased this century by about 0.6 degrees Celsius and are projected to rise by between 1.6 degrees and 3.8 degrees by 2100.
Dr. Leemans said China's reliance on coal-fired power for its industrial growth did not bode well for the world climate. "I think the political and economic powers in China are much greater than the environmental powers, and (greenhouse gas emissions) could accelerate," Dr. Leemans said. "China is not taking the problem seriously yet, although it is trying to incorporate this kind of research to see what is going to happen."
The climate change report, which will be released tomorrow, focuses on China but Mr David Melville of WWF-Hong Kong said some of the depressing scenarios could apply to the territory. Food supplies, for instance, could be affected by lower crop yields. "Maybe we could afford to import food from elsewhere but you have to keep in mind that the type of changes experienced in southern China will take place elsewhere as well," he said. Sea levels could rise as glaciers melted and the higher temperatures expanded the size of the oceans, threatening much of developed Hong Kong which is built on reclaimed land. Current projections are that sea levels worldwide will rise by 15 to 90 centimetres by 2100, depending on whether action is taken to reduce greenhouse gas emissions.
"Hong Kong has substantial areas built on reclaimed land and sea level rises could impact on that, not only on Chek Lap Kok but the West Kowloon Reclamation and the Central and Western Reclamation - the whole lot," Mr Melville said, adding that sea-walls would be needed. Depleted fresh water supplies would be another problem because increased evaporation would reduce levels. Mr Melville said the general outlook could be helped if Hong Kong used water less wastefully and encouraged energy efficiency to reduce fuel-burning. He also called on the West to help China improve its efficiency.