NORTHERN HEMISPHERE SNOW COVER (ALBEDO)
Snow has the very highest albedo- even higher than sea ice, reflecting as much as 90 percent of incoming solar radiation (NSIDC) .
The NASA 2002 Terra satellite global albedo image shows the huge extent and effect of far north snow aledo (deep red).
Snow cover and albedo loss in the Arctic is very large as reported by an ACAI 2008 update.
Regionally eqivalent to a doubling of CO2.
'Research findings since ACIA have quantified the contribution of feedback from changes in snow albedo to atmospheric warming. Chapin et al. (2005) found that a lengthening of the snow-free season in arctic Alaska over the last few decades, caused by terrestrial summer warming, has increased local atmospheric heating by about 3 watts/m2/decade. This is similar in magnitude to the regional warming expected from the predicted doubling of atmospheric carbon dioxide in the next few decades (4.4 watts/m2/decade). Across the entire Arctic region, feedback from changes in snow cover during 1970-2000 was simulated to have increased atmospheric heating by 0.9 watts/m2/decade Ekirchen et al. 2007). The snow cover climate feedback was enhanced by the fact that the snow cover changes were primarily due to earlier melt in the spring, when solar
radiation is stronger than during snow return in the fall.
Just recently, the total albedo loss calculated from sea ice and snow loss of the Arctic/subarctic region has doubled the estimates. The inclusion of snow in the models makes a huge difference.
As is it appears from the images opposite snow albedo is equivalent to sea ice albedo.
The NSIDC map of snow cover change opposite is compared to 1970
The 28 year trend in snow extent derived from visible and passive microwave satellite data indicates an annual decrease of approximately 1 to 3 percent per decade with greater deceases of approximately 3 to 5 percent during spring and summer. Precipitation in regions of seasonal snow cover appears to be constant or increasing slightly in some locations over the same time period, which suggests that diminishing snow cover is the result of increasing temperatures. One region where the snow appears to be diminishing rapidly is the Western United States, especially in spring when the duration of snow cover has been decreasing by 2-3 days per decade
According to David Robinson, head of the Rutgers Snow Cover Lab, a new pattern is emerging in which the Northern Hemisphere is cloaked in above-average snow during late autumn, winter, and early spring, followed by rapid melt and retreat in May and June. While snow cover varies from year to year, the far north has seen a clear trend towards less spring snow cover over the last thirty years.
A 2011 study by M. Flanner, which explains in detail the albedo of the northern hemisphere, finds it to be substantially larger than models have estimated (about double). The albedo has been decreasing over the past 30 years with about equal contributions from land clearing, snow decline and Arctic sea ice decline.
Far north snow cover is diminishing rapidly. This makes the total loss of far north albedo from all sources (glaciers, snow, sea ice) large and rapid.
Snow indirectly increases Arctic warming by way of black soot black carbon (soot) deposition from northern hemisphere air pollution emissions.
While summer sea ice has for long been recognised as a source of positive feedback to global warming resulting from global warming melting the sea ice and reducing the extent of reflective sea ice cooling albedo. There has been less attention to the loss of Arctic and subarctic snow loss through melting and its albedo change.
Seasonally, the area covered by snow in the NH ranges from a mean maximum in January of 45.2 × 106 km2 to a mean minimum in August of 1.9 × 106 km2 (1966–2004). Snow covers more than 33% of lands north of the equator from November to April, The role of snow in the climate system includes strong positive feedbacks related to albedo IPCC
The Rutgers Univ. Global Snow Lab has data on snow cover during the satellite era. Like most climate-related variables, snow cover shows a strong seasonal cycle, with more snow in winter and less in summer.
The declining trend is strongest when it really counts — when incoming sunlight is strongest during summer. In fact the downward trend in snow cover is strongest during the month of June, when solar input is also strongest:
The trend accounts for a net loss of over 5 million km^2 June snow cover since 1979. That’s considerably larger than the loss of Arctic sea ice over the same time span http://tamino.wordpress.com/2012/10/05/snow-2/
Oct 2012 research found that 2012 was a record year for loss of Arctic spring-summer snow cover. The snow is receding faster each year. The rate of loss of the snow is faster than that of the summer sea ice and is explained by NASA. .
Spring snow cover extent reductions in the 2008–2012 period exceeding climate model projections (C Derksen GRL 2012) shows statistically significant reductions in May and June spring terrestrial snow cover (when snow cover is mainly located over the Arctic).
Snow cover daily monthly
NASA video shows NH snow cycle .