Snow cover extent across the far northern latitudes for the month of June has steadily declined, especially since the mid 1990's. Data from the Rutgers University Snow Lab goes back to 1967.
Studies of snow cover published in Geophysical Research Letters and the Arctic Report Card: Update for 2012 found that, between 1979 and 2012, June snow cover extent decreased by 17.6 percent per decade compared to the 1979-2000 average.
In the Rutgers Global Snow Lab image below, above-average extent appears in shades of blue, and below-average extent appears in shades of orange. You can see that the below-average extent is much more common in recent years.
The snow-cover study authors, Chris Derksen and Ross Brown, found an overall decline in snow cover from 1967 through 2012, and also detected an acceleration of snow loss after the year 2003. (via NASA).
According to the NASA Earth Observatory article the Geophysical Research Letters study pointed out that declining snow cover raises ground temperatures and increases the thickness of the active layer-the uppermost layer of permafrost that thaws each summer. When organic material in thawing permafrost decomposes, it can release methane, a potent greenhouse gas when released to the atmosphere.
Climate model projections can become quite uncertain at more localized levels.
Arctic sea ice melt season trend this year.
Last month was the warmest of any month on record globally going back to the late 19th century.
Why hasn't global sea level rise accelerated over the past 20+ years?
Researchers recently compiled a new historical record of sea ice extent in the Arctic going back to the mid-19th century.
The annual "State of the Climate" report was just released and the results are quite sobering.