Arctic sea ice is melting — that, scientists can agree on. But why it's melting is a trickier question.
Climate change is part of it. But Arctic ice seems to be melting faster than climate models predicted it would.
Now, a group of scientists think they know why that is: variations in the temperature of the air circulating above the Arctic.
The key to the finding is a weather pattern called the North Atlantic Oscillation.
At times, the oscillation pushes the jet stream high, keeping the Arctic cool. But when it reverses, cool air can escape, and things begin to heat up.
The researchers think a reverse oscillation could be responsible for 30 to 50 percent of Arctic sea ice melt. But that still leaves climate change responsible to 50 to 70 percent.