A heatwave in the winter Arctic is forcing scientists to reconsider their most pessimistic forecasts of climate change.

While the heatwave could be a freak one-off, experts are concerned that global warming is eroding the polar vortex.

An influx of warm air has pushed temperatures in Siberia well over historical averages this month.

Greenland has experienced 61 hours above freezing so far in 2018 - more than three times as many hours as any other year on record.

“This is an anomaly among anomalies,” says Michael Mann, director of the Earth System Science Center at Pennsylvania State University.

“It is far enough outside the historical range that it is worrying – it is a suggestion that there are further surprises in store as we continue to poke the angry beast that is our climate.

“The Arctic has always been regarded as a bellwether because of the vicious circle that amplify human-caused warming in that particular region. And it is sending out a clear warning.”

“Spikes in temperature are part of the normal weather patterns – what has been unusual about this event is that it has persisted for so long and that it has been so warm,” says Ruth Mottram of the Danish Meteorological Institute.

“Going back to the late 1950s at least we have never seen such high temperatures in the high Arctic.”

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