The 2017 Milutin Milankovic Medal is awarded to Axel Timmermann for fundamental and pioneering contributions to the understanding of climate dynamics at different spatial and temporal scales.
Axel Timmermann represents a rare example of truly universal scientist who made significant contribution to understanding climate dynamics on very different spatial and temporal scales relevant both for past and future climate change. Timmermann graduated university as a theoretical physicist but then moved into the field of climate research where he has been very productive. In his PhD in meteorology he applied a dynamical-systems approach to study the predictability of the El Niño–Southern Oscillation (ENSO) and the study of ENSO remains among Timmermann’s primary scientific interests. However, over since his PhD, he has considerably diversified his research topics. Among them are the stability of the Atlantic meridional overturning circulation, abrupt climate change, climate-ice sheet interactions, response of the climate system to orbital forcing, interaction between biogeochemical cycles and ocean physics, and numerous other topics. Despite this diversity, Timmermann has been able to make a significant contribution in each of topic he has investigated. To solve the problems he has tackled, he has used a wide range of observations, models and mathematical tools. In particular, he has been able to successfully combine the results of complex general circulation models, Earth system models of intermediate complexity and the analysis of dynamical systems to show the full complexity of the system, as well as its most prominent characteristics that can be represented by a few differential equations. Unlike many others, Timmermann does not simply report model results but always extracts the more general underlying dynamical principles from the simulations he analyses. He has demonstrated over a decade that critical judgement and skillful applications of physical principles allow us to tackle the complexity of the climate system. Timmermann’s publication record is outstanding. He frequently signs as first author which is evidence of the fact that he is leading the research and keeps actively engaged in all aspects of the science. At the same time, he has established a sizable and effective research group at the University of Hawaii and he is strongly involved in teaching and supervising new generations of students and researchers. He also actively seeks and maintains effective collaborations with many colleagues internationally. He actively participated to several IPCC reports first as a contributing author and then as the lead author of the Fifth Assessment Report. From 2005 onwards he also contributed to the international programme Climate and Ocean: Variability, Predictability and Change (CLIVAR), for which he chaired the International CLIVAR Pacific Panel. In this role he has organised a number of meetings and workshops, furthering international research in this important area.