Michael Ghil (born 10 June 1944 in
Budapest, Hungary
Budapest (, ; ) is the capital and most populous city of Hungary. It is the ninth-largest city in the European Union by population within city limits and the second-largest city on the Danube river; the city has an estimated population of ...
)
is an
American
American(s) may refer to:
* American, something of, from, or related to the United States of America, commonly known as the "United States" or "America"
** Americans, citizens and nationals of the United States of America
** American ancestry, pe ...
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
Data assimilation is a mathematical discipline that seeks to optimally combine theory (usually in the form of a numerical model) with observations. There may be a number of different goals sought – for example, to determine the optimal state es ...
methodology.
He has systematically applied
dynamical systems theory
Dynamical systems theory is an area of mathematics used to describe the behavior of complex dynamical systems, usually by employing differential equations or difference equations. When differential equations are employed, the theory is called ' ...
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
Climate variability includes all the variations in the climate that last longer than individual weather events, whereas the term climate change only refers to those variations that persist for a longer period of time, typically decades or more ...
on many time scales have used a full hierarchy of
models
A model is an informative representation of an object, person or system. The term originally denoted the plans of a building in late 16th-century English, and derived via French and Italian ultimately from Latin ''modulus'', a measure.
Models c ...
, 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
Population dynamics is the type of mathematics used to model and study the size and age composition of populations as dynamical systems.
History
Population dynamics has traditionally been the dominant branch of mathematical biology, which has ...
,
macroeconomics
Macroeconomics (from the Greek prefix ''makro-'' meaning "large" + ''economics'') is a branch of economics dealing with performance, structure, behavior, and decision-making of an economy as a whole.
For example, using interest rates, taxes, and ...
, and the climate–economy–biosphere system.
He is currently a Distinguished Research Professor at the
University of California, Los Angeles
The University of California, Los Angeles (UCLA) is a public land-grant research university in Los Angeles, California. UCLA's academic roots were established in 1881 as a teachers college then known as the southern branch of the California St ...
and a Distinguished Professor Emeritus at the
École Normale Supérieure, Paris.
Early life and education
Ghil spent his childhood in
Romania
Romania ( ; ro, România ) is a country located at the crossroads of Central Europe, Central, Eastern Europe, Eastern, and Southeast Europe, Southeastern Europe. It borders Bulgaria to the south, Ukraine to the north, Hungary to the west, S ...
before moving to
Israel
Israel (; he, יִשְׂרָאֵל, ; ar, إِسْرَائِيل, ), officially the State of Israel ( he, מְדִינַת יִשְׂרָאֵל, label=none, translit=Medīnat Yīsrāʾēl; ), is a country in Western Asia. It is situated ...
.
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
The Courant Institute of Mathematical Sciences (commonly known as Courant or CIMS) is the mathematics research school of New York University (NYU), and is among the most prestigious mathematics schools and mathematical sciences research cente ...
, 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
Peter David Lax (born Lax Péter Dávid; 1 May 1926) is a Hungarian-born American mathematician and Abel Prize laureate working in the areas of pure and applied mathematics.
Lax has made important contributions to integrable systems, fluid dyn ...
(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
New York most commonly refers to:
* New York City, the most populous city in the United States, located in the state of New York
* New York (state), a state in the northeastern United States
New York may also refer to:
Film and television
* '' ...
, 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
The University of California, Los Angeles (UCLA) is a public land-grant research university in Los Angeles, California. UCLA's academic roots were established in 1881 as a teachers college then known as the southern branch of the California St ...
, 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 December 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
''Climate Dynamics'' is a peer-reviewed scientific journal published by Springer Science+Business Media. It covers all aspects of the dynamics of global climate systems, including analytical and numerical modeling research on the structure and be ...
. 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
A snowball is a spherical object made from snow, usually created by scooping snow with the hands, and pressing the snow together to compact it into a ball. Snowballs are often used in games such as snowball fights.
A snowball may also be a large ...
and warm states. Paleoclimatological evidence that the
Earth
Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's surfa ...
had indeed experienced snowball episodes in the
Pre-Cambrian
The Precambrian (or Pre-Cambrian, sometimes abbreviated pꞒ, or Cryptozoic) is the earliest part of Earth's history, set before the current Phanerozoic Eon. The Precambrian is so named because it preceded the Cambrian, the first period of the ...
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
Stochastic resonance (SR) is a phenomenon in which a signal that is normally too weak to be detected by a sensor, can be boosted by adding white noise to the signal, which contains a wide spectrum of frequencies. The frequencies in the white no ...
.
Throughout the 1980s and 1990s Ghil contributed to the development of
data assimilation
Data assimilation is a mathematical discipline that seeks to optimally combine theory (usually in the form of a numerical model) with observations. There may be a number of different goals sought – for example, to determine the optimal state es ...
techniques in
meteorology
Meteorology is a branch of the atmospheric sciences (which include atmospheric chemistry and physics) with a major focus on weather forecasting. The study of meteorology dates back millennia, though significant progress in meteorology did not ...
and
oceanography
Oceanography (), also known as oceanology and ocean science, is the scientific study of the oceans. It is an Earth science, which covers a wide range of topics, including ecosystem dynamics; ocean currents, waves, and geophysical fluid dynamic ...
, 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 method
Spectral methods are a class of techniques used in applied mathematics and scientific computing to numerically solve certain differential equations. The idea is to write the solution of the differential equation as a sum of certain " basis functio ...
s for the analysis of
chaotic
Chaotic was originally a Danish trading card game. It expanded to an online game in America which then became a television program based on the game. The program was able to be seen on 4Kids TV (Fox affiliates, nationwide), Jetix, The CW4Kid ...
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 equation
In mathematics, delay differential equations (DDEs) are a type of differential equation in which the derivative of the unknown function at a certain time is given in terms of the values of the function at previous times.
DDEs are also called time ...
s, and worked on the statistics and dynamics of
extreme events Rare or extreme events are events that occur with low frequency, and often refers to infrequent events that have widespread impact and which might destabilize systems (for example, stock markets, ocean wave intensity or optical fibers or society). ...
. Recently, Ghil proposed the
pullback attractor
In mathematics, the attractor of a random dynamical system may be loosely thought of as a set to which the system evolves after a long enough time. The basic idea is the same as for a deterministic dynamical system, but requires careful treatmen ...
as a mathematical framework able to encompass the
random
In common usage, randomness is the apparent or actual lack of pattern or predictability in events. A random sequence of events, symbols or steps often has no :wikt:order, order and does not follow an intelligible pattern or combination. Ind ...
and time-dependent nature of the
climate system
Earth's climate system is a complex system having five interacting components: the atmosphere (air), the hydrosphere (water), the cryosphere (ice and permafrost), the lithosphere (earth's upper rocky layer) and the biosphere (living things). '' ...
. 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.
Honors and awards
* 2022 American Physical Society Fellow
* 2012 A. Wegener Medal & Honorary Member, European Geosciences Union (EGU)
* 2010 Honorary Member, Hungarian Academy of Sciences
* 2005 Lorenz Lecture, American Geophysical Union
* 2005 Foreign Member, Austrian Academy of Sciences (OeAW)
* 2004 L. F. Richardson Medal, European Geosciences Union
* 2002 Honorary Fellow of the Royal Astronomical Society
* 1998 Member, Academia Europaea
*1995 Fellow, American Geophysical Union
* 1991 - 1992 Guggenheim Fellow
* 1988 Fellow, American Meteorological Society
Publications
A selection of books and papers is given below.
Selected books
* Bengtsson, L., M. Ghil, and E. Källén (Eds.), 1981: Dynamic Meteorology: Data Assimilation Methods, Springer-Verlag, New York/Heidelberg/Berlin, doi:10.1007/978-1-4612-5970-1, reissued as an eBook by Springer in 2012, e-ISBN 978-1-4612-5970-1, 330 pp.
* Ghil, M., R. Benzi, and G. Parisi (Eds.), 1985: Turbulence and Predictability in Geophysical Fluid Dynamics and Climate Dynamics, Proceedings of the International School of Physics “Enrico Fermi", Course LXXXVIII, Varenna, 1985, North-Holland Publ. Co., Amsterdam/New York/Tokyo, 449 pp.
* Ghil, M., and S. Childress, 1987: Topics in Geophysical Fluid Dynamics: Atmospheric Dynamics, Dynamo Theory and Climate Dynamics, Springer Science & Business Media, pp, doi:10.1007/978-1-4612-1052-8, ISBN 978-0-387-96475-l, reissued as an eBook by Springer in 2012,
ISBN 978-1-4612-1052-8, pp. xv + 485.
Selected papers
Theory of Climate Dynamics and Climate Variability
* Ghil, M., 1976: Climate stability for a Sellers-type model, J. Atmos. Sci., 33, 3–20.
* Ghil, M., and R. Vautard, 1991: Interdecadal oscillations and the warming trend in global temperature time series, Nature, 350, 324–327.
* Ghil, M., M. D. Chekroun, and E. Simonnet, 2008: Climate dynamics and fluid mechanics: Natural variability and related uncertainties, Physica D, 237, 2111–2126, doi:10.1016/j.physd.2008.03.036.
* Ghil, M., 2019: A century of nonlinearity in the geosciences, Earth & Space Science, 6, 1007–1042, doi: 10.1029/2019EA000599.
* Ghil, M., and V. Lucarini, 2020: The physics of climate variability and climate change, Rev. Mod. Phys., 92(3), 035002, doi:10.1103/RevModPhys.92.035002.
Paleoclimate
* Källén, E., C. Crafoord and M. Ghil, 1979: Free oscillations in a climate model with ice-sheet dynamics, J. Atmos. Sci., 36, 2292–2303,
https://doi.org/10.1175/1520-0469(1979)036%3C2292:FOIACM%3E2.0.CO;2
* Ghil, M., 1994: Cryothermodynamics: The chaotic dynamics of paleoclimate, ''Physica D'', 77, 130–159, doi: 10.1016/0167-2789(94)90131-7.
* Boers, N., M. Ghil and T. Stocker, 2022: Theoretical and paleoclimatic evidence for abrupt transitions in the Earth system, ''Envir. Res. Lett''., 17, 093006, doi: 10.1088/1748-9326/ac8944.
Data assimilation
* Ghil, M. and P. Malanotte-Rizzoli, 1991: Data assimilation in meteorology and oceanography, Adv. Geophys., 33, 141–266.
* Carrassi, A., M. Ghil, A. Trevisan and F. Uboldi, 2008: Data assimilation as a nonlinear dynamical systems problem: Stability and convergence of the prediction-assimilation system, ''Chaos'', 18(2), 023112, doi: 10.1063/1.2909862.
Blockings
* Legras, B., and M. Ghil, 1985: Persistent anomalies, blocking and variations in atmospheric predictability, J. Atmos. Sci., 42, 433–471.
Dynamical Systems Theory
* Chekroun, M. D., E. Simonnet, and M. Ghil, 2011: Stochastic climate dynamics: Random attractors and time-dependent invariant measures, Physica D, doi:10.1016/j.physd.2011.06.005.
* Ghil, M., 2017: The wind-driven ocean circulation: Applying dynamical systems theory to a climate problem, Discr. Cont. Dyn. Syst. – A, 37(1), 189–228, doi:10.3934/dcds.2017008.
* Charó, G. D., M. D. Chekroun, D. Sciamarella, and M. Ghil, 2021: Noise-driven topological changes in chaotic dynamics, ''Chaos,'' 31(10), doi:10.1063/5.0059461.
Macroeconomics & coupled climate-macroeconomics
* Hallegatte, S., and M. Ghil, 2008: Natural disasters impacting a macroeconomic model with endogenous dynamics, Ecological Economics, 68, 582–592, doi:10.1016/j.ecolecon.2008.05.022.
* Groth, A., and M. Ghil, 2017: Synchronization of world economic activity, Chaos, 27, 127002 (18 pp.), doi: 10.1063/1.5001820.
References
{{DEFAULTSORT:Ghil, Michael
Living people
University of California, Los Angeles faculty
American geophysicists
Academic staff of the École Normale Supérieure
Technion – Israel Institute of Technology alumni
Courant Institute of Mathematical Sciences alumni
Fellows of the American Meteorological Society
Fellows of the American Geophysical Union
1944 births