A United Nations scientific group has given its strongest warning yet about . The group is calling on governments to take urgent action to slow the production of industrial gases. Scientists say factory and motor vehicle pollution traps heat in the atmosphere. The U.N. report says that at the present rate, the condition could cause severe , starvation and the spread of disease within a century. They warn that millions of farm hectares will turn to desert. The U.N. report says poor countries would be hit hardest. But it also says Europe and the United States' Atlantic coast will face a growing risk of severe storms and flooding as temperatures rise.