The Year in Review: The planet
No denying the cold, hard facts
Michael McCarthy on climate change
Published: 28 December 2007
The sheer scale of what happened hasn't sunk in, it probably hasn't sunk in at all, with most people. They're not looking back on 2007 and talking about it, in the office, in pubs or over dinner. Listen to them: they're talking about Brown taking over from Blair, or David Cameron's prospects, or England failing to qualify for the European football championships. Or they're talking about getting and spending, or love and hate, as they always have. But what happened in September dwarfs all that.

You might compare it, in its implications, to Hitler marching his troops into the previously demilitarised Rhineland, in March 1936 – the clearest possible sign that the world was in for serious trouble. Some people understood the potential consequences of Hitler's move at once, but the world as a whole carried on with business as usual, until three years later the storm burst upon it. And so it seems to be with the ice.

On Sunday 16 September 2007, the sea ice covering the Arctic ocean melted back to a record low point. It has always melted back in the summer, but in recent years it has retreated further and further, to new lows, strongly suggesting the influence of climate change. The 2007 retreat, however, shattered the previous record, set only two years earlier, by a quite colossal amount, an amount so enormous as to be scarcely credible. It exceeded the September 2005 low point by another 22 per cent – an area of 1.2 million square kilometres, or more than 385,000 square miles. This represents an extra area of ice five times the size of the United Kingdom. Gone in a single summer. If you consider that and you don't think the world is rapidly warming up, what do you need to convince you?

This summer's Arctic melting astonished scientists around the world, and sent a chill down the backs of those who saw the implications. As the head of the Canadian Ice Service said, it wasn't predicted in any supercomputer-generated climate change scenario. The scale was entirely unexpected. It was not just the clearest signal yet that global warming is taking hold; it was an ominous indication that the warming process is proceeding far, far faster than anyone considered possible even five years ago, and that its catastrophic consequences may be upon us much sooner than we have hitherto imagined.

To take just one example: the rapid increase in the melt rate in the past two or three years has led to a revision of estimates of when the Arctic might be wholly ice-free in summer.

Early predictions by the UN's Intergovernmental Panel on Climate Change (IPCC), based on computer models of global warming, suggested that as climate change advances, this might happen by 2080. But now scientists are increasingly thinking the models have seriously underestimated the rate, and it may happen much earlier.

According to Mark Serreze, a researcher at the US National Snow and Ice Data Center (NSIDC) in Colorado, it might take only 25 years – or less. "If we were talking even two or three years ago, I'd have said the transition to an ice-free Arctic summer might be between 2070 and 2100," he said. "But we're starting to see that that is rather optimistic, and an educated guess right now would be 2030. It's something that could be within our lifetime."

He added: "We're on strong spiral of decline; some would say a death spiral. I wouldn't go that far but we're certainly on a fast track. We know there is a natural variability, but the magnitude of change is too great to be caused by natural variability alone."

Yet other estimates in recent months have put an ice-free Arctic summer even closer, perhaps within 10 years. This spells doom for much of the wildlife of the region, led by polar bears, which need the ice to hunt seals. Polar bears were officially notified as threatened species last year by being included in the Red List of the World Conservation Union. Some conservationists think they could be gone by mid-century.

What the melting of the Arctic ice will not do is add to global sea-level rise because, following Archimedes' principle, it is already displacing its own volume of water when floating in the sea. (When the ice-cube melts in the gin and tonic it does not raise the level of liquid in the glass.) It is the melting of giant land-based ice sheets, such as those covering Greenland and Antarctica, which is likely to add substantially to sea levels. But breathe no sigh of relief – this is also happening at an accelerating rate, and in 2007 there was an indication of it, just as graphic as the ice melt in the Arctic Ocean.

A new island appeared off the coast of Greenland. Several miles long, the island was once thought to be the tip of a peninsula halfway up Greenland's remote east coast, but a glacier joining it to the mainland melted away completely, leaving it surrounded by water.

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