LONDON -- When Al Gore predicted that climate change could lead to a 20-foot rise in sea levels, critics called him alarmist. After all, the International Panel on Climate Change, which receives input from top scientists, estimates surges of only 18 to 59 centimetres in the next century.

But a study led by James Hansen, the head of the climate science program at the National Aeronautics and Space Administration's Goddard Institute for Space Studies in New York and a professor at Columbia University, suggests that current estimates for how high the seas could rise are way off the mark - and that in the next 100 years melting ice could sink cities in the United States to Bangladesh.

Their argument goes like this: As the atmosphere warms and the ice caps melt, they will not melt in a consistent, gradual fashion. Rather, they will start to melt faster and faster as the century progresses,

"The first step should be a moratorium on new coal-fired power plants