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Julien Emile-Geay

Associate Professor of Earth Sciences

Contact Information
Phone: (213) 740-2945
Office: ZHS 275

Curriculum Vitae
Personal Website
Geosystems at USC

Biographical Sketch

To a mathematical mind bent on understanding nature, climate dynamics strikes an ideal blend of mathematics, physics, chemistry, geology, biology, and social sciences. I am also convinced that climate change is the greatest scientific issue of our time, so applying one's mind to the problem is not only fascinating, but also useful to society.


Ph.D. Climate Dynamics, Columbia University, 2006
M.S. Dynamics of Atmospheres and Oceans, Ecole Normale Supérieure, 2001
B.S. Earth Sciences, Ecole Normale Supérieure, 1999

Postdoctoral Training

Post-doctoral Fellow, Georgia Institute of Technology, 2007-2008   

Academic Appointment, Affiliation, and Employment History

Tenure Track Appointments

Assistant Professor, University of Southern California, 2008-2009   

PostDoctoral Appointments

Postdoctoral Fellow, Georgia Insitute of Technology, 2007-2008   
Postdoctoral Fellow, Georgia Insitute of Technology, 2006-2007   

Description of Research

Summary Statement of Research Interests

My research is primarily concerned with the role of the Tropics in long term climate variability. The central actor of this game is of course the El Niño-Southern Oscillation (ENSO) phenomenon, whose behavior I strive to understand on decadal to millennial timescales. Currently, this entails:

1) Reconstructing surface temperature conditions over the past 2 millennia, with a joint emphasis on proxy quality and the development of novel statistical methods. This work is at the interface between applied mathematics and climatology, in collaboration with Tapio Schneider (CalTech) and Bala Rajaratnam (Stanford).

2) Understanding and representing uncertainties in climate proxy records (by forward modeling the geological processes giving rise to such geochemical timeseries). This work is at the interface between applied geochemistry and climatology.

3) Modelling tropical climate over the past millennium, using an array of climate models with varying degrees of complexity. I am particularly interested in the climate sensitivity to natural (solar and volcanic) forcing and what it teaches us (or not) about climate sensitivity to anthropogenic greenhouse gas emissions.

4) Finally, I have a long-standing interest in the dynamical ocean response to geothermal heatflow. This work makes use of numerical models of the ocean (NEMO) and geochemical tracers that help constrain the patterns and intensity of the deep circulation, and its potential impact on millennial-scale climate change.

Research Keywords

ocean dynamics, atmospheric dynamics, climate dynamics, El Niño, last millennium, Hockey Stick, statistical climatology

Research Specialties

Mathematical Paleoclimatology, Climate modeling, data analysis

Funded Research

Contracts and Grants Awarded

Last Millennium Reanalysis Project (NOAA (Dept of Commerce)), Greg Hakim (UW), Julien Emile-Geay (USC), David Noone (U. Colorado), Eric Steig (UW), $1,488,473, 08/2014-  
GeoChronR – open-source tools for the analysis, visualization and integration of time-uncertain geos (National Science Foundation), N. McKay (Northern Arizona University), Julien Emile-Geay, Ken Collier, $566,000, 07/01/2014-  
LinkedEarth: Crowdsourcing Data Curation & Standards Development in Paleoclimatology (National Science Foundation), J. Emile-Geay, Y. Gil (ISI), Nick McKay (NAU), $798,000, 09/2015-08/2017  

Affiliations with Research Centers, Labs, and Other Institutions

Center for Applied Mathematical Sciences, Fellow,

Conferences and Other Presentations

Conference Presentations

"Probabilistic Models of Past Climate Change", Society for Industrial and Applied Mathematics, Talk/Oral Presentation, Abstract, Anaheim, CA, Invited, Spring 2012   
"The solar-ENSO connection: detection and implications", AGU Fall Meeting 2011, Talk/Oral Presentation, San Francisco, CA, AGU, Fall 2011   
"Pacific Decadal Variability in the view of linear equatorial wave theory", AGU Ocean Sciences, Talk/Oral Presentation, Portland, OR, 2010-2011   
"Variance-preserving, data-adaptive regularization schemes in RegEM. Application to ENSO reconstructions.", International Meeting in Statistical Climatology, Talk/Oral Presentation, Edinburgh, Scotland, 2010-2011   
"New mathematical tools for the analysis of incomplete climate data. Theory and applications", International Congress on Industrial and Applied Mathematics, Talk/Oral Presentation, Abstract, Vancouver, CA, SIAM, Invited, Spring 2011   
"Data-adaptive truncation in RegEM: potential for multiproxy reconstructions over the Common Era", AGU Fall Meeting 2010, Poster, San Francisco, CA, Fall 2010   
" Low-frequency tropical Pacific SST of the past millennium", American Geophysical Union, Talk/Oral Presentation, Abstract, San Francisco, Fall 2009   

Other Presentations

"The mathematics of paleoclimate reconstructions", CAMS weekly seminar, USC, Los Angeles, CA, Fall 2011   
"paleoclimate constraints on tropical Pacific dynamics", USC Paleoenvironment seminar, USC, Los Angeles, CA, Fall 2011   
"paleoclimate constraints on tropical Pacific dynamics ", Paleoclimate Modeling Inctercomparison Project, CLIVAR/PAGES, Villefranche-sur-mer, France, Fall 2011   
"Statistics for the Past Millennium The mathematics of climate change reconstructions", Statistics department seminar, Carnegie Mellon University, Pittsburgh, PA, Fall 2010   
"ENSO over the past millennium: reconstruction and error estimates", CalTech ESE seminar, California Institute of Technology, Pasadena, CA, Spring 2010   
"ENSO over the past millennium: reconstruction and error estimates", AOS seminar, UCLA, Los Angeles, CA, Spring 2010   
"Extracting the dynamical essence of geophysical timeseries", Quaternary Paleoecology Short Course, University of Minnesota, Minneapolis, MN, Spring 2010   
"Geothermal Heating : the Unsung Hero of the Abyssal Circulation", Earth Science Colloquium, USC, Zumberge Hall of Science, Spring 2009   
"Imputation of missing values in geophysical datasets: An improved, data-adaptive regularization scheme ", Probability and Statistics Seminar, USC, Center for Applied Mathematical Sciences, Spring 2009   


Journal Article

Emile-Geay, J., Eshleman, J. A. (2012). Towards a semantic web of paleoclimatology. Geochemistry, geophysics, geosystems.
Ault, T. R., Deser, C., Newman, M., Emile-Geay, J. (2012). Characterizing internal and forced low-frequency temperature variability in the equatorial Pacific during the last millennium. Geophysical Research Letters.
Cheetham, M., Feakins, S., Kirby, M., Emile-Geay, J., Lund, S., Zimmermann, S. (2011). 3000 Years of Interannual to Millennial Variability in Californian Runoff. Geophysical Research Letters.
Khider, D., Stott, L., Emile-Geay, J. (2011). Salinity influence on the Globigerinoides ruber Mg/Ca thermometer: assessing resulting uncertainties in paleoceanographic reconstructions. Paleoceanography.
Khider, D., Stott, L. D., Emile-Geay, J., Thunell, R., Hammond, D. (2011). Assessing El Niño Southern Oscillation Variability During the Past Millennium. Paleoceanography. Vol. 26, pp. 20. Cross ref
Emile-Geay, J., Cobb, K. M., Mann, M. E., Wittenberg, A. T. (2011). Estimating Tropical Pacific SST variability over the Past Millennium. Part 1: Methodology and Validation. Journal of Climate (American Meteorological Society).
Emile-Geay, J. T., Cobb, K. M., Mann, M. E., Wittenberg, A. T. (2011). Estimating Tropical Pacific SST variability over the Past Millennium. Part 2: Reconstructions and Uncertainties. Journal of Climate (American Meteorological Society).
Thompson, D. M., Ault, T. R., Evans, M. N., Cole, J. E., Emile-Geay, J. (2011). Comparison of observed and simulated tropical climate trends using a forward model of coral d18O. Geophysical Research Letters. (38) Cross ref
Emile-Geay, J. T., Schneider, T., Sima, D., Cobb, K. M., van Huffel, S., Wittenberg, A. T. (2011). Imputation of Missing Values in Climate Datasets: Data-Adaptive Truncation Schemes for RegEM. Journal of Climate (American Meteorological Society).


Other Advisement or Time Devoted to Students

Advising of Tiffany Tsai for research project and senior thesis, 09/01/2010-12/16/2011  
Advisement of Jill Hardy's undergraduate senior thesis. , 2010-2011   

Guest Lectures in Courses

JOUR 440: Environmental Journalism Guest lecture on climate change communication , Spring 2012   
GEOL505: Climate Dynamics @ USC, Fall 2011   
ENST150: Anthropogenic Global Warming: science and politics Guest lecture for Jim Haw, Fall 2010   

New Courses Developed

Introduction to Atmospheric Science, Earth Sciences, Elementary physical principles underlying the behavior of Earth’s atmosphere. Dry and moist thermodynamics, radiative transfer, conservation laws, fundamental dynamical balances, instability theory, cloud physics. This graduate-level course will introduce students to the basic workings of the atmospheric environment. After intro- ducing the relevant space and time scales, the class will introduce the basic thermodynamics, radiation theory, cloud micro- physics and fluid dynamics to enable a description and understanding of the elementary structure of the atmosphere, as well as fundamental phenomena like the Hadley circulation, midlatitude weather systems, planetary wave propagation, tropical cyclones, the ozone hole, and the greenhouse effect. , Fall 2010   
Data Analysis in the Earth & Environmental Sciences, Earth Sciences, Introduction to mathematical methods giving insight into Earth and Environmental data. Topics include : probability & statistics, timeseries analysis, spectral analysis, inverse theory, interpolation. (co-taught with Thorsten Becker)., Fall 2009   

Service to the University

Media, Alumni, and Community Relations

ABC News interview on heat waves, 2012-2013   

Other Service to the University

Hosted a screening of award-winning documentary "Carbon Nation', a Dornsife Commons event. , Fall 2011   
Panelist in the Global College Briefing on "What We Know about Climate Change", Spring 2011   
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