Until the noise of a century of media hype and unscientific speculation about the Arctic has been removed from the public debate, science will be unable to explain what, if anything, the signal from the Arctic is telling us.
In the last days of the Northern hemisphere’s summer, the sea ice that covers part of the Arctic Ocean reaches its minimum extent.
The annual change, recorded by satellites, has come to be seen as evidence of anthropogenic global warming, and a warning of what is to come.
It features in the global news every Summer. One journalist has called it the planet’s ‘white flag of surrender’, others the ‘Arctic Death Spiral’.
The lowest sea ice extent ever recorded was in 2012, and previous to that in 2007.
In the 2000s, a new trend of decreasing sea ice minimums seemed to be emerging. Whereas computer models had predicted that Arctic summer sea ice wouldn’t disappear until the middle of the century, the rate of decline seemed to be much faster.
The story of rapid, unnatural change and the plight of the polar bear became powerful symbols of climate change happening in real time. Campaigners launched high profile, swimming, kayaking and evidence-gathering missions to the North Pole to draw the media’s attention to the issue.
In 2007, media stories featured the claims of Prof. Wieslaw Maslowski, who claimed that the ice would be gone by 2013.
The following year, Mark Serreze, of the US National Snow and Ice Data Center (NSIDC) predicted that 2008 could be “become ice free at the North Pole this year.”
And in 2009, Al Gore announced ‘there is a 75 per cent chance that the entire north polar ice cap, during the summer months, could be completely ice-free within the next five to seven years.’
But the missions to the Arctic were hampered by bad weather, not open sea. And the dates by which climate scientists and politicians said the ice would disappear have come and gone, while the ice has remained.
Undaunted, fresh predictions have been made in every subsequent year.
2016 was no exception. In June, one scientist claimed that his prediction of an ice-free Arctic ocean might finally come true. The story made headlines throughout the world. But rather than disappearing, the joint-second lowest sea ice extent since 1978 was recorded.
This has caused controversy within climate science. A decade of failed predictions has signalled that science does not yet understand what drives variation in the Arctic. Some scientists have urged more caution. But the story of the Arctic’s ‘death spiral’ featured in news reports, in spite of these warnings.
And the story has a very long history.
In the 1950s, newspapers report the findings of an international panel of scientists. They predicted that the Arctic could be ice-free by the end of the 1970s.
Even as far back as the early 1920s, newspapers carried stories of a ‘great thaw’. One journalist wrote that ‘the giant ice cap has retreated as though in a flash’, adding that ‘the man of science breathes in our ear that outside of what has been described in Genesis there has been nothing like it in all history’.
By the 1970s concerns returned to the possibility of a new ice age, that would see the Arctic sea ice grow, making the Northern hemisphere inhospitable to agriculture.
One problem that persists is that there is still only a relatively short series of direct measurements on which to base our understanding of the Arctic.
Satellite monitoring of the Arctic only began in 1978, giving us less than forty years of reliable data. This may not be enough to establish what is normal – or abnormal – for the region.
The beginning of the satellite data starts at the end of a 40-year cooling phase, which may mean that our record of Arctic sea ice begins from an unusually high point.
Recent analysis of sea ice area shows that, although the last decade may have seen the most dramatic minimum extents, the decade that shows the greatest rate of decline occurred between 1998 and 2008 and that data since then shows significantly less decline.
And other explanations may better account for these observed changes than global warming.
One explanation for the more stable sea ice conditions seen since 2007 might be the Atlantic Multi-decadal Oscillation, or AMO – a natural cycle of warming and cooling. AMO peaked in 2008, and has recently entered a negative phase. The decline of summer sea ice may at least in part be a response to this and other natural cycles.
Rather than being based on an understanding of the Arctic’s climate, estimates of rapid sea ice decline have been made by simply drawing a straight line through the data. This may not be a safe way of making predictions, or of attributing sea ice decline to anthropogenic global warming.
As soon as the 2016 Arctic sea ice minimum was reached, it began its recovery, as it does every year. Even if we were to see an ice free summer Arctic, the significance of this event might be only symbolic.
Until the noise of a century of media hype and unscientific speculation about the Arctic has been removed from the public debate, science will be unable to explain what, if anything, the signal from the Arctic is telling us.