Hawking fears Earth could become like Venus

Asked about the environment, Hawking, who suffers from a degenerative disease, uses a wheelchair and speaks through a computerized voice synthesizer, said he was "very worried about global warming.''

He said he was afraid that Earth "might end up like Venus, at 250 degrees centigrade and raining sulfuric acid.''

The comment is a pointed one for China—which is the second largest emitter of the greenhouse gases that are blamed for global warming, after the United States. Experts warn that if emissions aren't reduced the world's glaciers could melt, threatening cities and triggering droughts and other environmental disasters.