Victor Brovkin¹, Lena Boysen¹, Julia Pongratz², Nicolas Vuichard³, Philippe P Peylin³ and David M Lawrence⁴, (1)Max Planck Institute for Meteorology, Hamburg, Germany, (2)Ludwig Maximilian University of Munich, Munich, Germany, (3)LSCE Laboratoire des Sciences du Climat et de l'Environnement, Gif-Sur-Yvette Cedex, France, (4)National Center for Atmospheric Research, Boulder, CO, United States