Another proposed technique that is starting to turn heads is the idea of increasing the albedo of buildings in order to reflect more sunlight. (carbonbrief.org)
Also, the reduction in forests caused by the ice's expansion increases albedo. (newworldencyclopedia.org)
It's negative because clearing rainforests to plant endless fields of identical crops increases the albedo, reflecting more sunlight and producing a slight cooling effect. (skepticalscience.com)