Glaciation of liquid clouds, snowfall and reduced cloud cover at industrial aerosol hot spots od Toll, V, Rahu, J, Keernik, H, Trofimov, H, Voormansik, T, Manshausen, P, Hung, E, Michelson, D, Christensen, M, Post, P, Junninen, H, Murray, BJ, Lohmann, U, Watson-Parris, D, Stier, P, Donaldson, N, Storelvmo, T, Kulmala, M, Bellouin, N