Michael Ghil

The 2012 Alfred Wegener Medal & Honorary Membership is awarded to Michael Ghil for his leading contributions to theoretical climate dynamics; his innovative observational studies involving model assimilation of satellite data in meteorology, oceanography and space physics; the breadth of his interdisciplinary studies, including macroeconomics; and also for his extensive supervision and mentoring of scores of graduate and postdoctoral students.

Michael Ghil is a world leader in the discipline of theoretical climate dynamics. He has applied systematically the ideas and methods from nonlinear dynamics, in particular, bifurcation theory and the ergodic theory of dynamical systems, to planetary-scale atmospheric and oceanic flows. He has used the successive-bifurcation approach (as presented in his 1987 book with Steve Childress and in many of his 275 research and review papers) to proceed from the analysis of simple flows with high temporal regularity and spatial symmetry, to the analysis of observed flows with their complex behaviour in space and time. His studies of climate variability on timescales ranging from intraseasonal to millennial have used a full hierarchy of models, from the simplest “toy” models through intermediate- complexity ones with hundreds of variables and on to atmospheric, oceanic and coupled general circulation models. Ghil’s modeling and theoretical studies have been complemented by careful and innovative observational studies on each of the timescales of interest. Over the past three decades, he has applied sequential estimation theory (Kalman filtering) to the model assimilation of satellite data in meteorology, oceanography and space physics and, most recently, to macroeconomics. Some of his former 70 graduate and postdoctoral students are now successfully applying this approach to the assimilation of satellite data from NASA and ESA missions, which will revolutionize our knowledge of Earth’s climate. Ghil’s other research achievements include a theory of forced paleoclimate oscillations that predicted the 6-7 kyr periodicity of Heinrich events five years before their discovery from observations; a theory of multiple weather regimes that connects them with intraseasonal oscillations in the extratropics; and a theory of the interannual variability of the the wind-driven double-gyre ocean circulation that has generated a rapidly growing literature over the past few years. Ghil has also led in the development of novel time series analysis tools (e.g., singular spectrum analysis) that provide a close connection between temporal regularities in a geophysical system, on the one hand, and its dynamical explanation and prediction, on the other. Ghil’s research, teaching and public service activities extend over four continents, but have been particularly evident in Europe. He has organized summer and winter schools in France, Hungary, Italy and Romania, and his former students and collaborators have included many European nationals, as well as Chinese, Japanese and Korean scholars. Among the many awards and honors that Ghil has received, of special interest to mention here are: Fellowship of both the American Meteorological Society and the American Geophysical Union, Membership of the Academia Europaea, the Austrian and the Hungarian Academy of Sciences, and the award of the L.F. Richardson Medal of EGU’s division of Nonlinear Processes in Geosciences. It is most appropriate and timely, therefore, that he be awarded the 2012 Alfred Wegener Medal and Honorary Membership in EGU.

Medal lecture video (Youtube) of the Alfred Wegener Medal given at the EGU General Assembly 2012.