The increased melting of Arctic ice is already driving extreme weather that affects hundreds of millions of people across North America, Europe and Asia, leading climate scientists have told the Guardian.
Severe winters are now strongly linked to soaring polar temperatures, say researchers, with deadly summer heatwaves and torrential floods also being linked. The scientists now fear the Arctic meltdown has instigated abrupt changes in the planet's swirling atmosphere, bringing extreme weather.
Global warming has been shrinking the northern ice cap, driving the loss of about three-quarters of its volume so far. But the recent heat in the Arctic has shocked scientists, with temperatures 33C above average in parts of the Russian Arctic and 20C higher in some other places.
In November, ice levels hit a record low, and we are now in "uncharted territory", said Prof Jennifer Francis, an Arctic climate expert at Rutgers in the US, who first became interested in the region when she sailed University through it on a round-the-world trip in the 1980s.
The chain of events that links the melting Arctic with weather to the south begins with rising global temperatures causing more sea ice to melt.
Unlike on the Antarctic continent, melting ice here exposes dark ocean beneath, which absorbs more sunlight than ice and warms further. This feedback loop is why the Arctic is heating up much faster than the rest of the planet.