Ralf Koppmann was until recently deputy director of the Institute for Chemistry and Dynamics of the Geosphere, Institute II: Troposphere at the Research Centre Jülich, Germany and is now Professor of Physics and head of the Atmospheric Physics Department at the University of Wuppertal, Germany. Contributors:Dr Lucy J. CarpenterDr Paolo CiccioliProf. Allen GoldsteinDr. Jacqui F. HamiltonProfessor. Thorsten HoffmannDr Alastair C. LewisDr Michela MannozziDr Simon O’DohertyDr. Stefan ReimannDr James RobertsDr. Jochen RudolphDr Paul ShepsonDr. Allison SteinerDr Joerg WarnkeDr. Jürgen WildtDr. Jonathan Williams