Leaders: Johanna Baehr (UHH), Lars Kutzbach (UHH), Jochem Marotzke (MPI-M).

Theme A provides the natural-science basis for understanding climate system dynamics, including climate variability and extremes, the climate change already unfolding, and the climate change expected for the future. Its projects will provide natural-science underpinning and specific information to Themes B and C.

A critical connection will exist with Themes B and C in that Theme A passes on information about irreducible (aleatoric) uncertainty due to internal variability, as well as regional predictions and information about variability including the probability of extreme events. Information passed on to C will additionally entail (multi-)decadal forecasts and the high-resolution climate results.

During a later stage, possibly a second funding phase of CLICCS, Theme A will generate and pass on projections refined by the insights of Theme B on social plausibility. Through interactions with Themes B and C, Theme A will advance model diagnostics to provide stakeholder-relevant parameters and climate information.

List of projects:

• A1 Carbon Dynamics in the Arctic
  Chairs: V. Brovkin (MPI-M), L. Kutzbach (UHH), D. Notz (UHH)
• A2 Clouds and Tropical Circulation
  Chairs: S. A. Buehler (UHH), B. Stevens (MPI-M)
• A3 Canopies in the Earth System
  Chairs: F. Ament (UHH), J. Behrens (UHH), B. Leitl (UHH), NN
• A4 African and Asian Monsoon Margins
  Chairs: J. Böhner (UHH), M. Claussen (UHH, MPI-M), G. Schmiedl (UHH)
• A5 The Land—Ocean Transition Zone
  Chairs: J. Hartmann (UHH), P. Korn (MPI-M), C. Schrum (HZG)
• A6 Earth System Variability and Predictability in a Changing Climate
  Chairs: J. Baehr (UHH), T. Ilyina (MPI-M), J.-S. von Storch (MPI-M), E. Zorita (HZG)