Human-caused climate change causes unprecedented Arctic heatwave, scientists say
Human-caused climate change is being held responsible for the warmest winter on record so-far at the North Pole.
The Arctic region reached record-high temperatures in November and ice coverage was the lowest in over 150 years.
Temperatures 15 degrees Celsius warmer than expected were recorded, in what a group of scientists have called an "unprecedented" heat wave.
In a December 21 report, the collective of climate researchers say it's a direct result of human-caused climate change.
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Dr Friederike Otto, a senior researcher at the University of Oxford's Environmental Change Institute, said they were "very confident" the warming was a result of human action.
"We have used several different climate modelling approaches and observations ... and in all our model, we find the same thing; we cannot model a heatwave like this without the anthropogenic signal," she told BBC News.
An early winter heat wave of -7C was recorded on November 11. That's 15C warmer than is expected for this time of year. Over the whole month, the temperature was on average 13C warmer than normal.
Temperatures have remained "well above normal", and the report forecasts the North Pole will again reach 15C warmer than is normal over Christmas.
Record-high temperatures mean record-low ice growth. November signals the beginning of Arctic ice growth; in 2016 the sea ice growth was the lowest since 1850. Typically, the North Pole is 95 per cent covered by sea ice, this year it's about 80 per cent covered.
"If the globe is warming, then the sea ice and ice on land [shrinks] then the darker water and land is exposed," Otto said.
"Then the sunlight is absorbed rather than reflected as it would be by the ice."
This creates a feedback loop; water absorbs more heat than ice, melting the ice it surrounds, which creates more water, which then heats, and melts more ice.
The researchers said modelling which reconstructed temperature patterns back "to about 1900" also show these temperatures are unprecedented.
In their modelling which removed historic human climate intervention, such a heatwave would occur roughly every 200 years.
Looking forward, the scientists predicted that such heat waves would occur about 50 per cent of the time by 2050.
"If nothing is done to slow climate change, by the time global warming reacher 2C, events like this winter would become common at the North Pole, happening every few years," the report said.
"That will be a huge stress on the ecosystem," Otto told BBC News.
The consequences of the warming Arctic climate are wide ranging. When the arctic heats up, weather patterns change around the region change.
It can mean an increase of rain on snow, which freezes into an ice crust. This crust prevents reindeer herds from finding food beneath the snow.
In 2013, an "extreme weather event" and subsequent ice crust caused the mass starvation of a herd, killing 61,000 reindeer - about 22 per cent of the herd.
According to the report, the Arctic is the fastest-warming region on the planet.