Julien Emile-Geay

Professor of Earth Sciences
Julien Emile-Geay
Pronouns He / Him / His Email julieneg@usc.edu Office ZHS 275 Office Phone (213) 740-2945

Research & Practice Areas

Climate Science, Climate modeling, Data Analysis & Semantics

Center, Institute & Lab Affiliations

  • Center for Applied Mathematical Sciences, Fellow


To a mathematical mind bent on understanding nature, climate dynamics strikes a perfect balance 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 critical to the survival of civilization as we know it.


  • 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 Scholar, Georgia Institute of Technology, 12/01/2006-11/30/2008
  • Tenure Track Appointments

    • Assistant Professor, University of Southern California, 2008-2009

    PostDoctoral Appointments

    • Postdoctoral Fellow, Georgia Insitute of Technology, 2007-20082007-2008
    • Postdoctoral Fellow, Georgia Insitute of Technology, 2006-20072006-2007
  • Summary Statement of Research Interests

    The climate system’s natural modes of variability are known to modulate its response to external stimuli (e.g. greenhouse gas emissions), in ways that either amplify or minimize societal impacts at the local scale. My work aims to better characterize such modes over the long term, test their theoretical understanding and their representation in climate models (GCMs), with the ultimate goal of reducing uncertainties in twenty-first century model projections. It requires the construction of new tools and their application to new data syntheses. My work lies at the interface between climate modeling, data analysis, and geoinformatics. Here are some of the topics my group is working on:

    1) Reconstructing climate conditions over the past 2 millennia. This we do by co-developing cutting-edge databases (PAGES2k), new statistical tools (GraphEM), or applying data-assimilation techniques to fuse models and observations

    2) Understanding and representing uncertainties in climate proxy records, by modeling the processes giving rise to what we observe in corals, stalagmites, lake & sediment cores, or trees.

    3) Understanding tropical climate, 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) Developing smart codes (GeoChronR) and databases (LinkedEarth) that allow to make optimal use of the data that my colleagues so painstakingly generate.

    Research Keywords

    climate dynamics, El Niño, last millennium, statistics, model/data comparison

  • Contracts and Grants Awarded

    • Last Millennium Reanalysis Project, (NOAA (Dept of Commerce)), Greg Hakim (UW) $1,488,473, 2013-CONT
    • GeoChronR – open-source tools for the analysis, visualization and integration of time-uncertain geos, (National Science Foundation), N. McKay (Northern Arizona University) $566,000, 2013-CONT
    • LinkedEarth: Crowdsourcing Data Curation & Standards Development in Paleoclimatology, (National Science Foundation), J. Emile-Geay $798,000, 2015-2017
  • Conference Presentations

    • “Probabilistic Models of Past Climate Change” , Society for Industrial and Applied MathematicsTalk/Oral Presentation, Invited, Anaheim, CA, Spring 2012
    • “The solar-ENSO connection: detection and implications” , AGU Fall Meeting 2011Talk/Oral Presentation, AGU, San Francisco, CA, Fall 2011
    • “Pacific Decadal Variability in the view of linear equatorial wave theory” , AGU Ocean SciencesTalk/Oral Presentation, Portland, OR, 2010-2011
    • “Variance-preserving, data-adaptive regularization schemes in RegEM. Application to ENSO reconstructions.” , International Meeting in Statistical ClimatologyTalk/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 MathematicsTalk/Oral Presentation, SIAM, Invited, Vancouver, CA, Spring 2011
    • “Data-adaptive truncation in RegEM: potential for multiproxy reconstructions over the Common Era” , AGU Fall Meeting 2010Poster, San Francisco, CA, Fall 2010
    • ” Low-frequency tropical Pacific SST of the past millennium” , American Geophysical UnionTalk/Oral Presentation, San Francisco, Fall 2009

    Other Presentations

    • “paleoclimate constraints on tropical Pacific dynamics”, USC Paleoenvironment seminar, Los Angeles, CA, 2011-2012
    • “paleoclimate constraints on tropical Pacific dynamics “, Paleoclimate Modeling Inctercomparison Project, Villefranche-sur-mer, France, 2011-2012
    • “The mathematics of paleoclimate reconstructions”, CAMS weekly seminar, Los Angeles, CA, 2011-2012
    • “Statistics for the Past Millennium The mathematics of climate change reconstructions”, Statistics department seminar, Pittsburgh, PA, 2010-2011
    • “ENSO over the past millennium: reconstruction and error estimates”, CalTech ESE seminar, Pasadena, CA, 2009-2010
    • “ENSO over the past millennium: reconstruction and error estimates”, AOS seminar, Los Angeles, CA, 2009-2010
    • “Extracting the dynamical essence of geophysical timeseries”, Quaternary Paleoecology Short Course, Minneapolis, MN, 2009-2010
    • “Geothermal Heating : the Unsung Hero of the Abyssal Circulation”, Earth Science Colloquium, Zumberge Hall of Science, 2008-2009
    • “Imputation of missing values in geophysical datasets: An improved, data-adaptive regularization scheme “, Probability and Statistics Seminar, Center for Applied Mathematical Sciences, 2008-2009
  • 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
      Advisement of Jill Hardy’s undergraduate senior thesis.
  • Media, Alumni, and Community Relations

    • ABC News interview on heat waves,

    Other Service to the University

    • Hosted a screening of award-winning documentary “Carbon Nation’, a Dornsife Commons event. , Spring Fall
    • Panelist in the Global College Briefing on “What We Know about Climate Change”, Spring Spri