Background
The authors write that "General Circulation Models (GCMs) are widely adopted tools to achieve future climate projections." They note, however, that "one needs to assess their accuracy, which is only possible by comparison of GCMs' control runs against past observed data," which they thus proceed to do in the case of snowfall regimes within the Italian Alps.

What was done
The two Italian researchers investigated the accuracy of simulations of snowfall throughout the Italian Alps that were provided by two GCMs (HadCM3, CCSM3), which are included within the family of models employed by the IPCC. This was done by comparing the models' output with a set of comprehensive ground data obtained from some 400 snow-gauging stations located within the region of interest for the period 1990-2009.

What was learned
Soncini and Bocchiola determined that "the investigated GCMs provide poor depiction of the snowfall timing and amount upon the Italian Alps," noting, in fact, that the HadCM3 model actually "displays considerable snowfall during summer," which they indicate "is clearly not supported by ground data." In addition, they report obtaining "contrasting results between the two models," with HadCM3 providing substantially constant volumes of snow received over time, and CCSM3 projecting decreasing snowfall volumes.

What it means
"Overall," in the words of the two researchers, "given the poor depiction of snowfall by the GCMs here tested, we suggest that care should be taken when using their outputs for predictive purposes." Or as we would suggest, the two models should probably not be used at all for predicting the future of snowfall in the Italian Alps or anywhere else for that matter.