Michael Ghil
Michael Ghil (born 10 June 1944 in Budapest, Hungary) is an American and European mathematician and physicist, focusing on the climate sciences and their interdisciplinary aspects. He is a founder of theoretical climate dynamics, as well as of advanced data assimilation methodology. He has systematically applied dynamical systems theory to planetary-scale flows, both atmospheric and oceanic. Ghil has used these methods to proceed from simple flows with high temporal regularity and spatial symmetry to the observed flows, with their complex behavior in space and time. His studies of climate variability on many time scales have used a  full hierarchy of models, from the simplest ‘toy’ models all the way to atmospheric, oceanic and coupled general circulation models. Recently, Ghil has also worked on modeling and data analysis in population dynamics, macroeconomics, and the climate–economy–biosphere system. He is currently a Distinguished Research Professor at the University of California, Los Angeles and a Distinguished Professor Emeritus at the École Normale Supérieure, Paris. Early life and education. Ghil spent his childhood in Romania before moving to Israel. He studied Mechanical Engineering at the Technion–Israel Institute of Technology, Haifa, Israel from where he received his B.Sc. in August  1966, and his M.Sc. in June 1971. He studied Mathematics at the Courant Institute of Mathematical Sciences, New York University, New York from where he received a Master’s in February 1973 and a Ph.D. in June 1975, under the supervision of Peter Lax (Abel Prize 2005). His doctoral dissertation title was “A Nonlinear Parabolic Equation with Applications to Climate Theory". Career. Ghil was affiliated with the Courant Institute of Mathematical Sciences, from September 1971 until May 1987, first as a Research Assistant (1971–1975) and then as a Research Professor (1982–1987), via intermediate appointments. While in New York, he was  a NAS/NRC Research Associate at the NASA Goddard Institute for Space Studies, New York from August 1975 to September 1976. In 1985 Ghil was appointed a full professor of Climate Dynamics at the Department of Atmospheric Sciences at the University of California, Los Angeles, where he also served as a Chairman of the same Department from September 1988 to June 1992. From July 1994 until June 2003 he was appointed Distinguished Professor of Climate Dynamics at UCLA, as well as the Director of the Institute of Geophysics & Planetary Physics, UCLA, from July 1992 until June 2003. He served as  the Director of the Environmental Research & Teaching Institute (CERES-ERTI), of École Normale Supérieure in Paris from November 2002 until September 2010 and as a Head of the Geosciences Department of ENS from July 2003 until Dec. 2009, where he was also a Distinguished Professor of Geosciences from September 2002 until September 2012. Since October 2003 until today, he is a Distinguished Research Professor of Atmospheric and Oceanic Sciences at the University of California, Los Angeles. He is also a Distinguished Professor Emeritus at École Normale Supérieure, Paris from September 2012. Research. Ghil has played an important role in the  foundations of modern theoretical climate dynamics. During the late 1970s, he worked in the application of dynamical systems theory to problems of the climate sciences. Starting from the work of Budyko and Sellers, Ghil proposed a 1D Energy Balance Model able to provide a succinct but essentially correct description of the climate system. Ghil’s analysis complemented the ones by Budyko and Sellers and played a key role for understanding the multistability of the Earth system, which features competing snowball and warm states. Paleoclimatological evidence that the Earth had indeed experienced snowball episodes in the Pre-Cambrian emerged in the  1990s. Energy balance models like Ghil’s, once supplemented with stochastic forcings (along the direction of Hasselmann’s programme) led to the discovery of phenomena like stochastic resonance. Throughout the 1980s and 1990s Ghil contributed to the development of data assimilation techniques in meteorology and oceanography, and to the theory of low-frequency variability of the atmosphere (with a special emphasis on the study of blocking), as well as to the understanding of large-scale ocean dynamics. He introduced the use of advanced spectral methods for the analysis of chaotic geophysical time series, and most prominently the singular-spectrum analysis  technique (SSA). In the 2000s, he extended his studies of the El Niño-Southern Oscillation phenomenon (ENSO) using Boolean delay and delay differential equations, and worked on the statistics and dynamics of extreme events. Recently, Ghil proposed the pullback attractor as a mathematical framework able to encompass the random and time-dependent nature of the climate system. Another area of research has been the development of data-driven methods for reconstructing the surrogate dynamics of partially observed systems. Additionally, he has contributed to data analysis and modeling in macroeconomics and population dynamics, as well as to coupled climate-economy-biosphere  modeling. Publications. A selection of books and papers is given below. Selected papers. Theory of Climate Dynamics and Climate Variability Data assimilation Blockings Dynamical Systems Theory