A powerful winter cyclone - the same storm that lead to two tornado outbreaks in the United States and disastrous river flooding - has driven the North Pole to the freezing point this week, 50 degrees above average for this time of year.

From Tuesday evening to Wednesday morning, a mind-boggling pressure drop was recorded in Iceland: 54 millibars in just 18 hours. This triples the criteria for "bomb" cyclogenesis, which meteorologists use to describe a rapidly intensifying mid-latitude storm. A "bomb" cyclone is defined as dropping one millibar per hour for 24 hours.