This pole-centred roundel of warm-in-cold is symptomatic of what climatologists call the negative phase of the Arctic oscillation (AO).

ECONOMIST: Britain��s cold snap is explained by the Arctic oscillation

When the Arctic Oscillation turns negative, that is, when the winds weaken, the cold air normally trapped around the North Pole surges south.

FORBES: 2011 Forecast: World Outperforms U.S., Europe Scuttles