The quantity of snow in a given location and time depends of course on snowfall but also on ablation. Both accumulation and ablation can, in the right conditions, respond to temperature changes. We survey observational studies of variability and trends in snow - most have shown declines that are consistent with local warming, and furthermore some studies have quantitatively demonstrated that warming is contributing to snow decline. The sensitivity to temperature is greatest in spring and least in mid-winter, especially in very cold locations.