Study of paleoclimate records indicates that high northern latitudes are experiencing unprecedented extreme temperatures not seen in the past 600 years.
Recent temperature extremes at high northern latitudes unprecedented in the past 600 years, Tingley M and Huybers P, Nature, 11 April 2013
Recent temperature extremes at high northern latitudes unprecedented in the past 600 years, Tingley M and Huybers P, Nature, 11 April 2013