The Earth's atmosphere hosts a vast range of phenomena that shape our everyday life and control the climate of the planet on timescales of a human being. Today's atmosphere has been altered substantially by humans releasing greenhouse gases and pollutants into the air that force environmental changes from the local to the global scale. Across these scales, we explore changes, gradients, and trends of atmospheric constituents and their isotope ratios to better understand how the physical and chemical processes in the atmosphere work, how humans interfere with the background state, and how the atmosphere connects to the biosphere, lands and oceans via the biogeochemical cycles. To this end, we develop new observation concepts, spectrometric sensors and imaging techniques that we deploy in the lab and in the field, in networks, on vehicles, aircraft, balloons, and satellites, and we devise complex simulation tools that help harvest our data for deeper insight. Our scientific focus is on the carbon and water cycles, air pollution and atmospheric photochemistry.
Water permeates all compartments of the environment and is a prerequisite for life on our planet. The transport of heat and substances tied to the hydrological cycle is of great importance for the climate system, the ecosystems, and global biogeochemical cycles. In addition, water, ice, and carbonates precipitated from water store information on the climate of the past. We study physical processes in aquatic systems such as lakes, groundwater, and the ocean, but also in the cryosphere as well as at the interface to the atmosphere. Central tools are the application and development of tracer and isotope methods, as well as numerical models to quantify transport and residence times in and between the system compartments. Isotopes and tracers also enable us to reconstruct and chronologically arrange past climatic and environmental conditions. Our research contributes to the fundamental understanding of the hydrological cycle and the climate system, as well as to a better management of water resources and aquatic ecosystems.
Understanding the Earth climate system, its natural variability and its anthropogenic future changes is a tremendous task, which implies observation and modelling across spatial and temporal scales and the study of various compartments (Ocean, Ice, Biosphere, Air, and Soil). We contribute to the study of the climate system in manifold ways. Observations and modelling of greenhouse gases help understand the atmosphere's energy balance and quantify human-induced and natural sources and sinks of those important constituents, i.e. their biogeochemical cycles, even in a distant past. The study of water isotopes permits estimates of precipitation and evaporation. The development of isotope toolboxes allows quantification of heat and matter transport. Through the study of climate archives, whether in the ocean, atmosphere, terrestrial systems or hydrosphere, we reveal natural global and regional climate change, the system's variability and sensitivity. To extract climate information from natural archives, we develop and apply isotope tracers, radiometric chronometers, and numerical simulations. We study the climate system in the field through campaigns and on our computers through models. We reach out from the North Pole, through remote caves and caverns, to the abyss of the oceans and the outer reaches of the troposphere.
Numerical models describe the processes in and interactions between atmosphere, ocean, biosphere and cryosphere using quantitative methods. The dynamics of the models are determined by physical equations and principles and thus, mirror our current understanding of the Earth system. The models are validated by running simulations of past events and comparing them to observations made during these events. Comparing model simulations with new observations made in the field and in the laboratory enables us to test and refine our understanding of the Earth system. As phenomena can range from a few meters to hundreds of kilometers, we run models of various scales from local to global. Finally, we can feed models with possible scenarios on emissions and climate drivers and impacts to predict future developments and to design optimal observation, mitigation and adaptation strategies.