Ice in the Arctic did something unusual last month. Its coverage – which reaches its annual lowest limit every September – stopped well short of the decline anticipated by meteorologists. Instead of dropping below the 3.4m square kilometres low it reached last year, the decrease in summer sea ice halted while still at a fairly respectable 5.1m square kilometres, bucking a trend of several years' ever-steepening decline. Now, as the winds and blizzards of the autumn Arctic re-appear, ice is spreading back across the frozen north.

And for climate change deniers that can only be regarded as good news. The fact that that Arctic sea ice has failed, by some margin, to reach its lowest extent shows that our world is not in peril after all, and that scientists are wrong, they claimed last week. The world is not really warming at all. Not surprisingly, these suggestions go down like a clutch of leaked emails with climate scientists. They insist the Earth is still warming. More and more heat is being trapped in our atmosphere by rising levels of carbon dioxide, the product of humanity's ever-increasing consumption of fossil fuels, a point backed by the most recent report of the Intergovernmental Panel on Climate Change. Last month it warned that it was now 95% certain humans were the cause of climate change, which could produce a devastating 2C rise in global temperatures in a few decades.

And one of the first catastrophic consequences of that rise will be the loss of sea ice in the Arctic in summer, it was stressed. Currently declining at about 1.5m square kilometres a decade, it may soon disappear altogether, with disastrous consequences for the region's wildlife, human populations and habitats.

As Mark Serreze, director of the US National Snow and Ice Data Centre, in Boulder, Colorado, puts it: "Without sea ice in summer, predators like polar bears and seals will have no platforms for hunting and the impact will go right down the food chain."

Explaining what is going on in the Arctic is therefore a task of considerable importance. The region is already feeling the effects of global warming more intensely than any other part of the world. Events in the region are therefore critical to understanding how our world is going to change. So why did sea ice cover not drop to a new low this year? What factors kept 5m square kilometres floating on the Arctic ocean when last year levels were down 4m? "The key factor is the meteorological equivalent of an egg-beater," says Serreze. "Most years, there is a vast area of high atmospheric pressure over the Beaufort Sea, just north of Alaska, with a corresponding area of low atmospheric pressure hanging over Siberia to the east. High pressure areas produce wind systems that rotate in a clockwise direction, while low pressure areas produce winds that rotate in an anti-clockwise direction."

The effect of these interlocking, counter-rotating wind systems is like an egg-beater that pulls warm air from the south and propels it north into the Arctic ocean. "On top of general global temperature rises, these warm winds have produced the record lows in sea ice cover in the Arctic in recent years," adds Serreze. But this September, the high pressure area of the Beaufort did not materialise and no warm winds were pulled into the Arctic. As a result, sea ice levels in September did not drop below their record minimum in 2012. Instead, they plateaued at a much higher level.

"However, we should be under no illusion about the general trend – and that is for the Arctic's sea ice cover to continue to decline decade by decade," says David Vaughan of the British Antarctic Survey. Key evidence for this argument is provided by satellite data, he adds. "We tend to think of satellites as very recent inventions but their use in monitoring Arctic sea ice is now in its fourth decade and virtually from the start their observations have shown that sea ice coverage is shrinking. More to the point, the only computer models that make sense of these observations are those that include anthropogenic warming, caused by the burning of fossil fuels, as a key factor."

In addition, there is the issue of ice volume. We can see Arctic ice cover is declining in extent in summer but is it also thinning? Or could it even be thickening? Europe's recently launched CryoSat2 probe carries an interferometric radar rangefinder that can measure the height difference between floating ice and open water and so determine ice thickness. Its data suggests ice volume is also disappearing at an alarmingly rapid rate.

So how long will it take until the summer ice is gone? This question was raised at a Royal Society symposium, Next Steps in Climate Science, earlier this month by Julienne Stroeve of the University of Colorado. "Many different computer models have been developed to predict when summer sea ice will disappear from the Arctic," she said. "Fifty per cent of these models say it will have gone by 2060. However, it is worth noting that the actual rate of ice loss now seems to be running about 20 years ahead of computer models, so I would think a better date will be between 2030 and 2040."

That does not mean that ice will disappear from the Arctic altogether. During the Arctic winter, ice cover has hardly changed in recent years, Serreze says. Nor is it likely to. "It is bitterly, bitterly cold in the Arctic winter and it would take an awful lot of the global warming to stop ice forming then. Arctic ice will be with us for hundreds and hundreds of years. It is only in summer, when temperatures hover around freezing, that the gradual warming produced by greenhouse gases can have an effect – and that is precisely what we are seeing now, albeit with an occasional blip in our graphs."