Lets assume that rising temperature follows a regular trajectory, and lets assume that there is a one-to-one correlation between temperature rise and its consequences. Such a regular trajectory is unlikely as the combination of growing C02-e, carbon and ice-melt feedbacks, solar cycles and stronger El Niño may join with extreme weather events and global tipping points to speed up this process.

Though we don’t understand many of the complexities, the simplicity of this calculation has a lot to recommend it.

With steady linear growth the earth will be heated to 1oC by 2012, and to 2oC by 2030.

Paleoclimatic evidence shows that for every 1oC rise we should expect a minimum 4-metre rise in sea levels.

We have just calculated that by 2030 the conditions will be in place to guarantee a minimal 8-metre sea level rise. With the usual inertial delays of thirty years or so built into the earth’s system, and applying a regular trajectory for sea levels as we did with temperature, we could be looking at 50cm rise within a decade and a full metre during the next.

During this time large areas of agricultural land will be gradually flooded, in Egypt, Bangladesh, northern China and the Philippines. Florida, Boston and London will be badly affected, as will Melbourne and much of our coastline.

Food production will be lessened as the Himalayan glaciers melt, there will be a lot less to fish and land will be lost to drought and sea. In the same period global population will rise by one billion, most living in cities.

This is a recipe for catastrophe if we dont prepare.

We are fully aware of the refugee crisis that would follow such sea-level rise, and the likelihood that there wuld be war.

However we vary the parameters, this process shows we have run out of time and should prepare now for what cannot be prevented if we wish to preserve a planet similar to that on which civilisation developed and to which life on earth is adapted.

A National Risk Assessment Council is needed to prepare citizens for the changes that are coming, (Source John James (Planet extinction.com))

The 2C figure is significant because this is level of warming that is likely to be adopted as the threshold to be avoided by the UN climate negotiations in Copenhagen – although small islands states and developing nations have argued that 1.5C would be a more appropriate target.

Nine metres of sea level rise is higher than anything predicted so far because the new study takes into account the potential that the Greenland and west Antarctic ice sheets start to melt as the Earth warms. This did not factor into the most recent assessment of the state of climate science by the Intergovernmental Panel on Climate Change (IPCC) in 2007. It forecast a sea-level rise of up to 59cm by 2100, and between 4-6m in the next few hundred years, if average global temperatures stabilised around 2C.

“Everybody’s known that the IPCC’s last numbers were underestimates because they didn’t include all the factors that can accelerate ice sheet melting,” said Robert Kopp of Princeton University, who led the latest study. “If the future models are limited, you want to look at other approaches to get at the question of sea-level rise one approach is to turn to the past record of sea-level rise.”

Kopp’s team reconstructed the sea levels in the last interglacial period, around 125,000 years ago. At the time, polar temperatures were around 3-5C warmer and equatorial sea-surface temperatures were around 2.5-3.5C warmer than today. “So you look at things like coral reef terraces and how high they grew and, if you know something about the ecology of corals, you can say how high sea level was relative to the top of the coral reef. Or you look at old beaches that are now stranded above the sea-line, or you look at sediments that have textures that indicate they were deposited inter-tidally.”

His results, published in the journal Nature, showed that sea levels around the world during the last interglacial were between 6.6m and 9m higher than today. “During this period when temperatures were 2-3C above pre-industrial levels, global sea level looks like it was very likely at least 6.6m higher than today, which implies significant melting of the Greenland and west Antarctic ice sheets.”

Kopp said the results could be used to infer what could happen to future sea levels over the next few hundred years, as a result of human-induced global warming. “The warming we’re on track to do now is more than enough to commit us to last-interglacial levels of sea-level rise.”

Kopp’s work echoes recent research by the Scientific Committee on Antarctic Research (SCAR) suggesting that sea-levels could rise much higher than predicted by the IPCC by the end of the century. The study by SCAR suggested that sea levels could rise by up to 1.4m by 2100 if the Antarctic ice began to melt.