What was done
In the words of the authors, "a new Global Synoptic Data Network consisting of 2100 stations within the boundaries of the former Soviet Union created jointly by the [U.S.] National Climatic Data Center and Russian Institute for Hydrometeorological Information was used to assess the climatology of snow cover, frozen and unfrozen ground reports, and their temporal variability for the period from 1936 to 2004."

What was learned
Groisman et al. report that "during the past 69 years (1936-2004 period), an increase in duration [our italics] of the period with snow on the ground over Russia and the Russian polar region north of the Arctic circle has been documented by 5 days or 3% and 12 days or 5%, respectively," and they note that this result "is in agreement with other findings."

What it means
In commenting on this finding and the similar findings of others, the five researchers say that "changes in snow cover extent during the 1936-2004 period cannot [our italics] be linked with 'warming' (particularly with the Arctic warming)." And why? Because, as they continue, "in this particular period the Arctic warming was absent [our italics]."

These facts are particularly enlightening, because approximately 70% of the atmospheric CO2 increase experienced since the dawn of the Industrial Revolution occurred between 1934 and 2004, yet over this time period, and throughout the part of the planet where climate models predict CO2-induced global warming should be both strongest and most evident (the Arctic), there was no warming, CO2-induced or otherwise, which means that the lion's share of the Arctic warming of the past century or more occurred in concert with the initial 30% increase in the atmosphere's CO2 concentration, yet this is the period during which climate alarmists generally attribute most of the warming that occurred to natural causes, and if this is true, it suggests that the Arctic has experienced little CO2-induced warming throughout any of the period during which the earth was recovering from the naturally-induced Little Ice Age, which leaves us with little reason to worry about anthropogenic CO2 emissions, as they appear to have had next to no impact on the climate of the most sensitive part of the planet throughout historic time.