Peer Reviewed Study: "Earth today stands in imminent peril"

Six scientists from some of the leading scientific institutions in the United States have issued what amounts to an unambiguous warning to the world: civilisation itself is threatened by global warming.

They also implicitly criticise the UN's Intergovernmental Panel on Climate Change (IPCC) for underestimating the scale of sea-level rises this century as a result of melting glaciers and polar ice sheets.

Instead of sea levels rising by about 40 centimetres, as the IPCC predicts in one of its computer forecasts, the true rise might be as great as several metres by 2100. That is why, they say, planet Earth today is in "imminent peril".

In a densely referenced scientific paper published in the Philosophical Transactions of the Royal Society A some of the world's leading climate researchers describe in detail why they believe that humanity can no longer afford to ignore the "gravest threat" of climate change.

"Recent greenhouse gas emissions place the Earth perilously close to dramatic climate change that could run out of control, with great dangers for humans and other creatures," the scientists say. Only intense efforts to curb man-made emissions of carbon dioxide emissions and other greenhouse gases can keep the climate within or near the range of the past one million years, they add.

The researchers were led by James Hansen, the director of Nasa's Goddard Institute for Space Studies, who was the first scientist to warn the US Congress about global warming.

The other scientists were Makiko Sato, Pushker Kharecha and Gary Russell, also of the Goddard Institute, David Lea of the University of California, Santa Barbara, and Mark Siddall of the Lamont-Doherty Earth Observatory at Columbia University in New York.

In their 29-page paper, "Climate Change and trace gases", the scientists frequently stray from the non-emotional language of science to emphasise the scale of the problems and dangers posed by climate change.

In an email to The Independent, Dr Hansen said: "In my opinion, among our papers this one probably does the best job of making clear that the Earth is getting perilously close to climate changes that could run out of our control."

The unnatural "forcing" of the climate as a result of man-made emissions of carbon dioxide and other greenhouse gases threatens to generate a "flip" in the climate that could "spark a cataclysm" in the massive ice sheets of Antarctica and Greenland, the scientists write.