Will oceans surge 59 centimetres this century – or 25 metres?

The new climate: a controversial study suggests rapid polar meltdown and rising sea levels

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.


“If we follow ‘business-as-usual’ growth of greenhouse gas emissions,” he writes in an e-mail interview, “I think that we will lock in a guaranteed sea-level rise of several metres, which, frankly, means that all hell is going to break loose.”

The scientific basis for this idea – which Prof. Hansen and five co-authors gleaned from geological records, ice core samples and analysis of the sea floor – is outlined in a recent paper published by the British journal Philosophical Transactions of the Royal Society.

In stark contrast to estimates put forward by the IPCC, Prof. Hansen and his colleagues argue that rapidly melting ice caps in Antarctica and Greenland could cause oceans to swell several metres by 2100 – or maybe even as much as 25 metres, which is how much higher the oceans sat about three million years ago.

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, quickly reaching a point where they could disappear altogether. This is because of “positive feedback” effects – factors that create a loop of exacerbated melting and global warming.

The Globe and Mail