
The speech by former US Vice-President Al Gore was apocalyptic. ‘The North Polar ice cap is falling off a cliff,’ he said. ‘It could be completely gone in summer in as little as seven years. Seven years from now.’

Those comments came in 2007 as Mr Gore accepted the Nobel Peace Prize for his campaigning on climate change.

But seven years after his warning, The Mail on Sunday can reveal that, far from vanishing, the Arctic ice cap has expanded for the second year in succession – with a surge, depending on how you measure it, of between 43 and 63 per cent since 2012.

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To put it another way, an area the size of Alaska, America’s biggest state, was open water two years ago, but is again now covered by ice.

The most widely used measurements of Arctic ice extent are the daily satellite readings issued by the US National Snow and Ice Data Center, which is co-funded by Nasa. These reveal that – while the long-term trend still shows a decline – last Monday, August 25, the area of the Arctic Ocean with at least 15 per cent ice cover was 5.62 million square kilometres.

This was the highest level recorded on that date since 2006 (see graph, right), and represents an increase of 1.71 million square kilometres over the past two years – an impressive 43 per cent.

Other figures from the Danish Meteorological Institute suggest that the growth has been even more dramatic. Using a different measure, the area with at least 30 per cent ice cover, these reveal a 63 per cent rise – from 2.7 million to 4.4 million square kilometres.

The satellite images published here are taken from a further authoritative source, the University of Illinois’s Cryosphere project.

They show that as well as becoming more extensive, the ice has grown more concentrated, with the purple areas – denoting regions where the ice pack is most dense – increasing markedly.

Crucially, the ice is also thicker, and therefore more resilient to future melting. Professor Andrew Shepherd, of Leeds University and University Coillege, London, an expert in climate satellite monitoring, said yesterday: ‘It is clear from the measurements we have collected that the Arctic sea ice has experienced a significant recovery in thickness over the past year.

‘It seems that an unusually cool summer in 2013 allowed more ice to survive through to last winter. This means that the Arctic sea ice pack is thicker and stronger than usual, and this should be taken into account when making predictions of its future extent.’

The speech by former US Vice-President Al Gore (above) was apocalyptic. He said that the North Polar ice cap is falling off a cliff and could be gone in seven years

Yet for years, many have been claiming that the Arctic is in an ‘irrevocable death spiral’, with imminent ice-free summers bound to trigger further disasters. These include gigantic releases of methane into the atmosphere from frozen Arctic deposits, and accelerated global warming caused by the fact that heat from the sun will no longer be reflected back by the ice into space.

Judith Curry, professor of earth and atmospheric sciences at Georgia Institute of Technology in Atlanta, said last night: ‘The Arctic sea ice spiral of death seems to have reversed.’

Those who just a few years ago were warning of ice-free summers by 2014 included US Secretary of State John Kerry, who made the same bogus prediction in 2009, while Mr Gore has repeated it numerous times – notably in a speech to world leaders at the UN climate conference in Copenhagen in 2009, in an effort to persuade them to agree a new emissions treaty.

The ice cap is falling off a cliff. It could be completely gone in summer in as little as 7 years from now

Mr Gore – whose office yesterday failed to respond to a request for comment – insisted then: ‘There is a 75 per cent chance that the entire polar ice cap during some of the summer months could be completely ice-free within five to seven years.’

Misleading as such forecasts are, some people continue to make them. Only last month, while giving evidence to a House of Lords Select Committee inquiry on the Arctic, Cambridge University’s Professor Peter Wadhams claimed that although the Arctic is not ice-free this year, it will be by September 2015.

Asked about this yesterday, he said: ‘I still think that it is very likely that by mid-September 2015, the ice area will be less than one million square kilometres – the official designation of ice-free, implying only a fringe of floes around the coastlines. That is where the trend is taking us.’

For that prediction to come true it would require by far the fastest loss of ice in history. It would also fly in the face of a report last year by the UN Intergovernmental Panel on Climate Change (IPCC), which stated with ‘medium confidence’ that ice levels would ‘likely’ fall below one million square kilometres by 2050.

Politicians such as Al Gore have often insisted that climate science is ‘settled’ and have accused those who question their forecasts of being climate change ‘deniers’.

However, while few scientists doubt that carbon-dioxide emissions cause global warming, and that this has caused Arctic ice to decline, there remains much uncertainty about the speed of melting and how much of it is due to human activity. But outside the scientific community, the more pessimistic views have attracted most attention. For example, Prof Wadhams’s forecasts have been cited widely by newspapers and the BBC. But many reject them.

An area twice the size of Alaska was open water two years ago and is now covered in ice after the arctic ice cap has expanded for the second year in a row

Yesterday Dr Ed Hawkins, who leads an Arctic ice research team at Reading University, said: ‘Peter Wadhams’s views are quite extreme compared to the views of many other climate scientists, and also compared to what the IPCC report says.’

Dr Hawkins warned against reading too much into ice increase over the past two years on the grounds that 2012 was an ‘extreme low’, triggered by freak weather.

‘I’m uncomfortable with the idea of people saying the ice has bounced back,’ he said.

However, Dr Hawkins added that the decline seen in recent years was not caused only by global warming. It was, he said, intensified by ‘natural variability’ – shifts in factors such as the temperature of the oceans. This, he said, has happened before, such as in the 1920s and 1930s, when ‘there was likely some sea ice retreat’.

Dr Hawkins said: ‘There is undoubtedly some natural variability on top of the long-term downwards trend caused by the overall warming. This variability has probably contributed somewhat to the post-2000 steep declining trend, although the human-caused component still dominates.’

Like many scientists, Dr Hawkins said these natural processes may be cyclical. If and when they go into reverse, they will cool, not warm, the Arctic, in which case, he said, ‘a decade with no declining trend’ in ice cover would be ‘entirely plausible’.

Peer-reviewed research suggests that at least until 2005, natural variability was responsible for half the ice decline. But exactly how big its influence is remains an open question – and as both Dr Hawkins and Prof Curry agreed, establishing this is critical to making predictions about the Arctic’s future.

Prof Curry said: ‘I suspect that the portion of the decline in the sea ice attributable to natural variability could be even larger than half.

‘I think the natural variability component of Arctic sea ice extent is in the process of bottoming out, with a reversal to start within the next decade. And when it does, the reversal period could last for several decades.’

This led her to believe that the IPCC forecast, like Al Gore’s, was too pessimistic.

‘Ice-free in 2050 is a possible scenario, but I don’t think it is a likely scenario,’ she concluded.