When the polar vortex stumbles, the weather at ground level can pivot from mild to brutal in a matter of days. A circulation ...

(CNN) — High above the North Pole, in a slice of atmosphere rarely noticed and even less understood, a transformation is underway. Over the next 10 days, changes in the stratosphere will upend weather ...

(CNN) — High above the North Pole, in a slice of atmosphere rarely noticed and even less understood, a transformation is underway. Over the next 10 days, changes in the stratosphere will upend weather ...

(CNN) — It’s really, really cold again — as the US shivers through at least the eighth blast of air from the Arctic this winter. Winter, which is warming faster than any other season for much of the ...

Editor's note: CNN’s Laura Paddison contributed to this report. (CNN) — It’s really, really cold again — as the US shivers through at least the eighth blast of air from the Arctic this winter. Winter, ...