| 2009- |
Member, Scientific Advisory Board, Alfred-Wegener-Institute for Polar and Marine Research, Bremerhaven |
| 2008- |
Member, MISTRA SWECIA Scientific Reference Group, Sweden |
| 2008- |
Member, Wissenschaftlicher Beirat, Nordwest-Verbund Meeresforschung, Bremen |
| 2008- |
Member, Scientific Committee for the Bayer Climate Award |
| 2008 |
Member, Süring Foundation, Board of Trustees |
| 2007- |
Chair, Excellence Cluster on Integrated Climate System Analysis and Prediction |
| 2006- |
Chair of the COSMOS (community Earth System Models) network |
| 2005-2008 |
Süring Foundation, Vice Chair |
| 2003-2009 |
Member of the DFG (German Science Foundation) Senate and Joint Committee (Hauptausschuss) |
| 2003-2008 |
Chair of the German Meteorological Society (Deutsche Meteorologische Gesellschaft), since 2006: Vice Chair |
| 2003-2006 |
Member of the steering committee (Präsidium) of the GeoUnion - Alfred Wegener foundation (Alfred Wegener Stiftung) |
| 2001-2006 |
Member of the National Committee on Global Change Research (German Science Foundation - DFG) |
| 2000-2005 |
Member of the IGBP - GAIM task force (International Geosphere-Biosphere Programme - Global Analysis, Integration and Modelling) |
| 2000-2003 |
Member of the CLIVAR-PAGES task force (CLIVAR: Climate Variability, core project of the World Climate Research Programme, PAGES: Past Global Changes, an IGBP- core project) |
| 1999-2003 |
Member of BMBF-Sachverständigenkreises Globale Umweltaspekte (scientific advisory of the federal ministry of education and research on questions related to global change) |
| 1999-2002 |
Chair of the Section (Zweigverein) Berlin / Brandenburg of the German Meteorological Society (Deutschen Meteorologischen Gesellschaft) |
| 1998-2004 |
Member of the research advisory committee of IGES (Institute for Global Enviromental Strategies) Kanagawa, Japan |
| 1998-2001 |
Member of the Europäische Akademie zur Erforschung von Folgen wissenschaftlich- technischer Entwicklungen, Bad Neuenahr-Ahrweiler |
| 1997-2002 |
Member of the scientific steering committee of BAHC (Biological Aspects of the Hydrological Cycle - an IGBP core project) |
| 1996-2001 |
Scientific advisor (climate) of World Wide Fund WWF, Germany |
| 1995-1998 |
Member of the steering committee of the IIASA (International Institute of Applied System Analysis, Laxenburg, Austria) Land Use Change Project |
| 1995-1998 |
Member of the advisory board of LITFASS (Lindenberg Inhomogenous Terrain - Fluxes between Atmosphere and Surface - a Long-term Study) - a project of the German Weather Service, DWD |
| 1993-1997 |
Member of the BALTEX (Baltic Sea Experiment) - a core project of the Global Energy and Water Cycle Experiment GEWEX within the World Climate Research Programme WCRP - Working Group on Process Studies |
