Six Degrees: Our Future on a Hotter Planet. Mark Lynas

climate forcing scenarios would lead to a disastrous multi-metre sea level rise on the century time scale.’ If the ice sheet melt rate doubles each decade, a serious possibility, the resulting sea level rise will total 5 metres by 2100, he points out.

      So perhaps James Hansen's warnings should be taken more seriously, particularly his concern that melt rates and sea level rise could speed up dramatically over the century to come. An early warning is already out there: sea levels are currently rising at 3.3 mm a year-much faster than the 2.2 mm projected by the IPCC's 2001 report. If, as Hansen suggests is likely, melt rates as rapid as those at the end of the last ice age begin to happen again this century, the whole Greenland ice sheet could disappear within 140 years. The geography of the world's coastlines would then look radically different. Miami would disappear entirely, as would most of Manhattan. Central London would be flooded. Bangkok, Bombay and Shanghai would also lose most of their area. In all, half of humanity would have to move to higher ground, leaving landscapes, buildings and monuments that have been central to civilisation for over a thousand years to be gradually consumed by the sea.

       Last stand of the polar bear

      Not everyone sees the transformation of the Arctic as a bad thing. Even as water sluices off the melting Greenland ice sheet, climate change at the top of the world could be making some people very rich. Pat Broe hopes to be one of them. An American entrepreneur, in 1997 Broe bought the run-down north Canadian port of Churchill for the princely sum of $7. For the fewer than a thousand residents who live in this drab-looking town, life has been tough-even in a place which has rebranded itself as the ‘Polar Bear Capital of the World’.

      But according to Broe, boom times lie just around the corner. As the polar ice melts, humble little Churchill could become an important hub in lucrative shipping routes opening up between Asia, Europe and North America across waters that used to be permanently frozen. Which is just as well, because by the time these shipping routes open, the Polar Bear Capital of the World will be looking for another raison d'être-for the simple reason that as the sea ice disappears, so will the polar bears.

      One rather unamusing irony of global warming is that the retreat of the northern polar ice cap is sparking a new petroleum gold rush, bringing further fossil fuels onto world markets which-when burned-will inevitably make the climate change problem worse. According to some estimates, a quarter of the world's undiscovered oil and gas reserves lie under the Arctic Ocean, in areas which have historically been seen as undrillable because of thick drifting ice floes. Massive investments are already being made to tap into this economically valuable resource: the Norwegian government is spending billions of dollars building a liquefied natural gas terminal at the far northern port of Hammerfest, whilst a massive gas find in Russian Arctic waters-estimated to contain double Canada's entire reserves-has sparked an unseemly scramble amongst oil majors to partner with Russia's giant Gazprom corporation to exploit it. According to one energy analyst quoted in the New York Times, this new Arctic rush is ‘the Great Game in a cold climate’.

      Internationally, Arctic Ocean nations Canada, Denmark, the United States, Norway and Russia are battling to establish undersea mineral rights to ‘their’ sections of the seabed. In August 2007 Russian explorers mounted a particularly audacious land grab by piloting a submersible under the ice and planting a rustproof metal flag on the seabed 4,000 metres below the North Pole-thereby claiming the entire area, and its fossil fuel riches, for the motherland. ‘We are happy that we placed a Russian flag on the ocean bed, and I don't give a damn what some foreign individuals think about that,’ declared expedition leader Artur Chilingarov haughtily as he returned to a hero's welcome-complete with champagne and ranting pro-Kremlin youth groups-in Moscow. Stretching unintended irony to breaking point, the triumphant Chilingarov was then handed a large furry toy polar bear-the emblem of the pro-Putin party United Russia (of which Chilingarov is a parliamentary deputy)-as a military brass band played. The US State Department was studiously unmoved, however: ‘A metal flag, a rubber flag or a bedsheet on the ocean floor… doesn't have any legal standing,’ a spokesman told Reuters. ‘You can't go around the world and just plant flags and say “We're claiming this territory,”’ complained an annoyed Canadian foreign minister, accusing Russia of behaving like a fifteenth-century colonial explorer.