"The heavy snowfalls this month have been used as fodder for ridicule by those who argue that global warming is a myth, yet scientists have long pointed out that warmer global temperatures have been increasing the rate of evaporation from the oceans, putting significantly more moisture into the atmosphere — thus causing heavier downfalls of both rain and snow in particular regions, including the Northeastern United States."
However, the NOAA Climate Scene Investigators (CSI), a team of “attribution” experts whose job is to determine the causes for climate conditions, "found no evidence — no human “fingerprints” — to implicate our involvement in the snowstorms. If global warming was the culprit, the team would have expected to find a gradual increase in heavy snowstorms in the mid-Atlantic region as temperatures rose during the past century. But historical analysis revealed no such increase in snowfall. Nor did the CSI team find any indication of an upward trend in winter precipitation along the eastern seaboard.
Annual Snowfall Reagan National Airport 1888-2010 shows no trendThe CSI Team found abundant historical evidence of heavy mid-Atlantic snowstorms whenever an El Niño and a negative NAO acted in concert, further supporting their conclusion that the record-setting snowstorms were the result of natural causes. But could global warming have elevated the potency of this dynamic duo? Again, the CSI Team didn’t find a connection.
But the extreme blocked-NAO of this past winter was opposite to the trend toward more positive phases of the NAO since 1950, and also opposite to projections for a positive trend in the NAO during the 21st Century due to greenhouse gas increases.
The observed variations of winter precipitation in the Washington, D.C., area (left) have been very different from what models predict would occur if only human-induced emissions of greenhouse gas and aerosols (right) were taken into consideration. This evidence suggests the mid-Atlantic’s trends in precipitation are mainly due to natural variability, not human influence."
For more on the unreliability of General Circulation Climate Models, see the highly recommended piece A Climate of Belief in Skeptic Magazine.