It's not even summer in the Northern Hemisphere, and an unusual heat wave at the North Pole is sending temperatures up to the melting point. 

Zero degrees Celsius is about 17 to 19 degrees warmer than the North Pole is supposed to be at this time of year.  The overall region north of 80 degrees latitude is about 10 Celsius above the normal of -16 Celsius.  Scientists are concerned that the heat wave could hasten melting at a time the Arctic Ice cap has shrunk to nearly the smallest extent on record.

Such temperature spikes have been historically rare.  But this episode is the fourth in the past five years.

The combination of warmer temperatures and shrinking ice are in all likelihood are connected to the buildup of greenhouse gases in the atmosphere from human activities.  Last week, the US National Oceanic and Atmospheric Administration (NOAA) released a study that found that an "extraordinary heat" that affected the Arctic in 2016 "could not have happened without the steep increases in greenhouse gas concentrations".