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Michael Ghil
Born	(1944-06-10)June 10, 1944 Budapest, Hungary
Alma mater	Technion – Israel Institute of Technology, Courant Institute of Mathematical Sciences
Known for	Boolean Delay Equations, Climate Dynamics, Data Assimilation, Energy Balance Model, El Niño-Southern Oscillation, Application of Dynamical Systems Theory to Geophysical Problems, Reduced Order Models, Singular Spectrum Analysis
Awards	A. Wegener Medal, 2005 Lorenz Lecture, L. F. Richardson Medal
Scientific career
Fields	Climate Science
Institutions	University of California, Los Angeles, École normale supérieure
Thesis	(1975)
Doctoral advisor	Peter Lax
Notable students	Hervé Le Treut

Michael Ghil (born 10 June 1944) 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

Michael Ghil was born in Budapest, Hungary in June 10, 1944. He spent his childhood and teenage 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 (both cum laude). He was also a research assistant and module instructor during these years. He then 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, several of his most influential works dealt with 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 made seminal contributions 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 pioneered 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 innovative Boolean delay and delay differential equations, and worked on the statistics and dynamics of extreme events. 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 global climate models. 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.

Mentoring

Ghil has supervised over 35 PhD students, with a total of over 85 descendants.

Former Ph.D. students include E. Källén (1980), S. E. Cohn (1982), D. P. Dee (1983), B. Legras (1983), A. P. Mullhaupt (1984), H. Le Treut (1985), G. Wolansky (1985), M. Kimoto (1989), F. Varadi (1989), R. Todling (1992), Y. Sezginar Unal (1994), D. Paillard (1995), M. D. Dettinger (1997), S. Koo (2001), G. Bellon (2004), M. D. Chekroun (2009); E. Chavez (2013); K.B.Z. Ogutu (2015); C. Colon (2016); D. Walwer (2018).

Ghil has also supervised the work of more than 40 post-docs and junior visiting scientists.

Among those, one can mentioned K. P. Bube (1978–80), J. J. Tribbia (1984), R. N. Miller (1985), H. Itoh (1986), R. Vautard (1987–89), C. Penland (1988–89), M. Kimoto (1990–91), F.-f. Jin (1988–93), R. Fu (1991–93), A. W. Robertson (1992–93), S. Speich (1992–94), P. Yiou (1996-97), F. Lott (1997–98), A. Wirth (1997–99), M. Karaca (1998–1999), S. Kravtsov (1998–2001), C.-j. Sun (1998–2000), L. U. Sushama (1999–2000), Y. Tian (1999–2000), D. Kondrashov (1999-2000), E. Simonnet (2001–02), B. Coluzzi (2005–2009), A. Groth (2007–2013), H. Liu (2013–2015), N. Boers (2015–2017), W. Bagniewski (2020–); E. Bach (2021–).

Honors and Awards

Michael Ghil holds numerous Honors and Awards, a list of some is given below.

• A. Wegener Medal & Honorary Member, European Geosciences Union (EGU), 2012
• Honorary Member, Hungarian Academy of Sciences, 2010
• 2007 P. D. Thompson Lecturer, National Center for Atmospheric Research, Boulder, Colorado
• 2005 Lorenz Lecture, American Geophysical Union
• 2005 Foreign Member, Austrian Academy of Sciences (OeAW)

• 2004 L. F. Richardson Medal, European Geosciences Union
• 2004 G. Lemaître Chair, Université Catholique de Louvain, Belgium
• 2004 Honorary Member, Academy of Engineering Sciences, Romania (AST-R)
• 2002 Associate (i.e., Honorary Member), Royal Astronomical Society
• 1998 Member, Academia Europaea
• 1997 Visiting Chair and Medal, Collège de France, Paris
• 1996 Elf-Aquitaine/CNRS Chair and Medal, Académie des Sciences, Paris
• 1995 Condorcet Chair and Medal, Ecole Normale Supérieure, Paris
• 1995 Fellow, American Geophysical Union
• 1993 - 1995 and 1998 - 2000 NSF Special Creativity Awards
• 1991 - 1992 Guggenheim Fellow,
• 1988 Fellow, American Meteorological Society
• 1985 – 2002 Distinguished Visiting Scientist, Jet Propulsion Laboratory, Caltech/NASA

Publications

Ghil has published over 350 articles and a dozen books, a selection of which is given below. He is a highly cited researcher with h-index = 63 in ISI Web of Science as of Nov. 17, 2021. A list of publications can be found here and here.

Selected Books

1. Bengtsson, L., M. Ghil, and E. Källén (Eds.), 1981: Dynamic Meteorology: Data Assimilation Methods, Springer-Verlag, New York/Heidelberg/Berlin, 330 pp.

2. Ghil, M., R. Benzi, and G. Parisi (Eds.), 1985: Turbulence and Predictability in Geophysical Fluid Dynamics and Climate Dynamics, North-Holland Publ. Co., Amsterdam/New York/Tokyo, 449 pp.

3. Ghil, M., and S. Childress, 1987: Topics in Geophysical Fluid Dynamics: Atmospheric Dynamics, Dynamo Theory and Climate Dynamics, Springer Science & Business Media; reissued as an eBook by Springer in 2012, xv + 485 pp, doi:10.1007/978-1-4612-1052-8, ISBN 978-0-387-96475-l, ISBN 978-1-4612-1052-8 (eBook).

Selected Papers

1. Ghil, M., 1976: Climate stability for a Sellers-type model, J. Atmos. Sci., 33, 3–20.
2. Legras, B., and M. Ghil, 1985: Persistent anomalies, blocking and variations in atmospheric predictability, J. Atmos. Sci., 42, 433–471.
3. Ghil, M., and R. Vautard, 1991: Interdecadal oscillations and the warming trend in global temperature time series, Nature, 350, 324–327.
4. Ghil, M. and P. Malanotte-Rizzoli, 1991: Data assimilation in meteorology and oceanography, Adv. Geophys., 33, 141–266.
5. Ghil, M., 2001: Hilbert problems for the geosciences in the 21st century, Nonlin. Proc. Geophys., 8, 211–222, https://doi.org/10.5194/npg-8-211-2001.
6. 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.
7. 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.
8. 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.
9. 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.
10. Ghil, M., 2019: A century of nonlinearity in the geosciences, Earth & Space Science, 6, 1007–1042, doi: 10.1029/2019EA000599.
11. 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.
12. 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.

References

1. "Michael Ghil" (PDF). Retrieved 7 July 2020.
2. "Michael Ghil - The Mathematics Genealogy Project". www.genealogy.math.ndsu.nodak.edu. Retrieved 2021-12-16.
3. Budyko, M. I. (1969-01-01). "The effect of solar radiation variations on the climate of the Earth". Tellus. 21 (5): 611–619. doi:10.3402/tellusa.v21i5.10109. ISSN 0040-2826.
4. Sellers, William D. (1969-06-01). "A Global Climatic Model Based on the Energy Balance of the Earth-Atmosphere System". Journal of Applied Meteorology and Climatology. 8 (3): 392–400. doi:10.1175/1520-0450(1969)008<0392:AGCMBO>2.0.CO;2. ISSN 1520-0450.
5. Ghil, Michael (1976-01-01). "Climate Stability for a Sellers-Type Model". Journal of the Atmospheric Sciences. 33 (1): 3–20. doi:10.1175/1520-0469(1976)033<0003:CSFAST>2.0.CO;2. ISSN 0022-4928.
6. Hoffman, Paul F.; Kaufman, Alan J.; Halverson, Galen P.; Schrag, Daniel P. (1998-08-28). "A Neoproterozoic Snowball Earth". Science. 281 (5381): 1342–1346. doi:10.1126/science.281.5381.1342.
7. Benzi, R; Sutera, A; Vulpiani, A (1981-11-01). "The mechanism of stochastic resonance". Journal of Physics A: Mathematical and General. 14 (11): L453 – L457. doi:10.1088/0305-4470/14/11/006. ISSN 0305-4470.
8. Ghil, Michael; Malanotte-Rizzoli, Paola (1991-01-01), Dmowska, Renata; Saltzman, Barry (eds.), "Data Assimilation in Meteorology and Oceanography", Advances in Geophysics, vol. 33, Elsevier, pp. 141–266, doi:10.1016/s0065-2687(08)60442-2, retrieved 2021-12-16
9. Legras, B.; Ghil, M. (1985-03-01). "Persistent Anomalies, Blocking and Variations in Atmospheric Predictability". Journal of the Atmospheric Sciences. 42 (5): 433–471. doi:10.1175/1520-0469(1985)042<0433:PABAVI>2.0.CO;2. ISSN 0022-4928.
10. Ghil, M.; Vautard, R. (1991-03). "Interdecadal oscillations and the warming trend in global temperature time series". Nature. 350 (6316): 324–327. doi:10.1038/350324a0. ISSN 1476-4687. {{cite journal}}: Check date values in: |date= (help)
11. Jin, Fei-Fei; Neelin, J. David; Ghil, Michael (1994-04-01). "El Niño on the Devil's Staircase: Annual Subharmonic Steps to Chaos". Science. 264 (5155): 70–72. doi:10.1126/science.264.5155.70.
12. Vautard, Robert; Yiou, Pascal; Ghil, Michael (1992-09-15). "Singular-spectrum analysis: A toolkit for short, noisy chaotic signals". Physica D: Nonlinear Phenomena. 58 (1): 95–126. doi:10.1016/0167-2789(92)90103-T. ISSN 0167-2789.
13. Ghil, M.; Allen, M. R.; Dettinger, M. D.; Ide, K.; Kondrashov, D.; Mann, M. E.; Robertson, A. W.; Saunders, A.; Tian, Y.; Varadi, F.; Yiou, P. (2002). "Advanced Spectral Methods for Climatic Time Series". Reviews of Geophysics. 40 (1): 3–1–3-41. doi:10.1029/2000RG000092. ISSN 1944-9208.
14. Zaliapin, Ilya; Keilis-Borok, Vladimir; Ghil, Michael (2003-05-01). "A Boolean Delay Equation Model of Colliding Cascades. Part II: Prediction of Critical Transitions". Journal of Statistical Physics. 111 (3): 839–861. doi:10.1023/A:1022802432590. ISSN 1572-9613.
15. Ghil, Michael; Zaliapin, Ilya; Coluzzi, Barbara (2008-12-01). "Boolean delay equations: A simple way of looking at complex systems". Physica D: Nonlinear Phenomena. 237 (23): 2967–2986. doi:10.1016/j.physd.2008.07.006. ISSN 0167-2789.
16. Ghil, M.; Yiou, P.; Hallegatte, S.; Malamud, B. D.; Naveau, P.; Soloviev, A.; Friederichs, P.; Keilis-Borok, V.; Kondrashov, D.; Kossobokov, V.; Mestre, O. (2011-05-18). "Extreme events: dynamics, statistics and prediction". Nonlinear Processes in Geophysics. 18 (3): 295–350. doi:10.5194/npg-18-295-2011. ISSN 1023-5809.{{cite journal}}: CS1 maint: unflagged free DOI (link)
17. ^ Chavez, Mario; Ghil, Michael; Urrutia-Fucugauchi, Jaime, eds. (2015-12-18). "Extreme Events". Geophysical Monograph Series. doi:10.1002/9781119157052. ISSN 2328-8779.
18. Ghil, Michael; Chekroun, Mickaël D.; Simonnet, Eric (2008-08-15). "Climate dynamics and fluid mechanics: Natural variability and related uncertainties". Physica D: Nonlinear Phenomena. Euler Equations: 250 Years On. 237 (14): 2111–2126. doi:10.1016/j.physd.2008.03.036. ISSN 0167-2789.
19. Ghil, Michael; Lucarini, Valerio (2020-07-31). "The physics of climate variability and climate change". Reviews of Modern Physics. 92 (3): 035002. doi:10.1103/RevModPhys.92.035002.
20. Chekroun, Mickaël D.; Simonnet, Eric; Ghil, Michael (2011-10-15). "Stochastic climate dynamics: Random attractors and time-dependent invariant measures". Physica D: Nonlinear Phenomena. 240 (21): 1685–1700. doi:10.1016/j.physd.2011.06.005. ISSN 0167-2789.
21. Santos Gutiérrez, Manuel; Lucarini, Valerio; Chekroun, Mickaël D.; Ghil, Michael (2021-05-01). "Reduced-order models for coupled dynamical systems: Data-driven methods and the Koopman operator". Chaos: An Interdisciplinary Journal of Nonlinear Science. 31 (5): 053116. doi:10.1063/5.0039496. ISSN 1054-1500.
22. Ghil, Michael (2017). "The wind-driven ocean circulation: Applying dynamical systems theory to a climate problem". Discrete & Continuous Dynamical Systems. 37 (1): 189. doi:10.3934/dcds.2017008.
23. Groth, Andreas; Ghil, Michael (2017-12-01). "Synchronization of world economic activity". Chaos: An Interdisciplinary Journal of Nonlinear Science. 27 (12): 127002. doi:10.1063/1.5001820. ISSN 1054-1500.

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