To understand the changing climate of our Earth, climate physics not only analyzes weather statistics, it focuses on the interaction between the different components of the climate system. The working group climate physics at the Meteorological Institute and the department “The land in the earth system” at the Max Planck Institute for Meteorology investigate the role of the terrestrial biosphere in the climate system. Guiding questions include: How do forests, steppes and dry lands respond to the changing climate, and, in turn, how do changes in vegetation pattern affect climate? Do shifts in vegetation amplify or dampen climate change? How did the interaction between vegetation and climate change throughout the history of the Earth’s climate? How has anthropogenic land use and land cover change affected regional and global climate? These questions are being tackled by using comprehensive models of the global climate system. Satellite based data and in-situ measurements help evaluating model results.