You can polish them clear. The more expensive way is to use a plastic polish like Meguiar’s PlastX. Just rub on with a sponge, then remove with a soft cloth.
Or, the cheaper and almost as effective method is using a small amount of regular toothpaste. Just do the same thing, smear on, rub off (removal seems to work better if you use a bit of water on the lens, either spit or snow or whatever.) Just repeat whatever you do every six months or so, or as needed.