Northern Hemisphere Snow Cover is Retreating Snow cover extent provided by the Rutgers University Global Snow Laboratory (GSL) is available from 1967–2016 for the North America + Greenland, Northern Hemisphere, Eurasia, and North America. All anomalies are relative to the 1981–2010 average. | Northern Hemisphere average annual snow cover has declined in recent decades. This pattern is consistent with warmer global temperatures. Some of the largest declines have been observed in the spring and summer months. |