Research aims at quantifying the relative importance of atmospheric and oceanic processes in controlling climate variability and climate change on a large range of timescales: from monthly, through decadal, to centennial and millennial timescales. We maintain a strong focus on modeling the complex atmosphere-ocean interactions to understand the atmospheric and oceanic role in climate variability on this wide range of timescales. We study internal variability that is often associated with dynamical modes such as the Madden Julian Oscillation (MJO), the North Atlantic Oscillation (NAO), the El Niño/Southern Oscillation (ENSO), the Atlantic Multidecadal Variability (AMV) or the Pacific Decadal Variability (PDV) that superimpose the red background spectrum, as well as the climate response to (natural and anthropogenic) external forcing. The study area ranges from the middle atmosphere to the sea surface and through the whole water column of the ocean.