Klaus Hasselmann

The 2002 Vilhelm Bjerknes Medal is awarded to Klaus Hasselmann for his pioneering contributions to the theory and modelling of ocean-atmosphere interaction and climate variability, which have improved our ability to predict ocean waves and detect climate change.

Prof. Klaus Hasselmann is a pioneer in atmosphere-ocean interaction and one of the fathers of modern climate research. He was the driving force behind the development of complex coupled atmosphere-ocean models which were applied to the problems of natural climate variability and anthropogenic climate change. He was the first to describe climate variability by the interaction of the different climate subsystems, in particular the atmosphere and the ocean. He realised the analogy to Brownian motion in statistical physics and showed that the rapidly varying atmosphere can induce low-frequency variability in the oceans.

Hasselmann is also one of the leading statisticians in atmospheric sciences. He developed concepts to simplify complex dynamical systems (e.g. Principal Interaction Patterns and Principal Oscillation Patterns) and to detect an anthropogenic climate signal against the background noise.

Hasselmann was one of the first to understand the role of nonlinear interactions in the formation of natural surface wave fields and the first who derived the energy evolution equation (also known as the kinetic equation) of complex surface wave systems. The generalization of these results represented basic progress in the general theory of stochastic wave processes. A few years later he organised and supervised the JONSWAP wave project that became a most important milestone in our understanding of surface wave properties. The wave modelling complex WAM that was created on the basis of the energy evolution equation and the observational knowledge from JONSWAP have become standard tools used in many institutions.