Let's just wait a few more decades to be sure though. It would be a waste spending resources trying to prevent the demise of life on Earth when we didn't need to.
According to official US Weather Bureau records (pdf) from 1922, there was open sailing very close to the North Pole that year. Anthony Watts unearthed this quote from the Weather Bureau:
"In fact, so little ice has never before been noted. The expedition all but established a record, sailing as far north as 81 degrees in ice-free water."
"Long term" is misleading and relevant only to a space age start point where we launched satellites.
2000 year ice core samples:
http://www.theregister.co.uk/2013/04/15/western_antarctic_me...
Longer records exist in ships logs showing that ships sailed through an ice-free arctic.
http://www.theregister.co.uk/2008/07/03/goddard_polar_ice?pa...
According to official US Weather Bureau records (pdf) from 1922, there was open sailing very close to the North Pole that year. Anthony Watts unearthed this quote from the Weather Bureau:
"In fact, so little ice has never before been noted. The expedition all but established a record, sailing as far north as 81 degrees in ice-free water."
So much lower extent than today.