Dark surfaces absorb more light while light surfaces reflect it. Extremely large areas of ice and snow reflect more light (and its energy) back into space than dark areas such as the ocean or ground that would be exposed if the ice and snow were to melt.

Since the idea of global warming is based on the fact that the atmosphere is building up a layer of pollutants that essentially let UV light in but does not let IR(heat) out I would say that dark surfaces would contribute to global warming as they absorb light and give off heat. Where as lighter surfaces reflect light instead of transferring it into heat.