Nathan M. Urban

I am an Energy Security Fellow in the Energy Security Center at Los Alamos National Laboratory. I no longer work at Princeton University.

My research centers on global climate change from an Earth system perspective, with an emphasis on Bayesian data-model calibration, probabilistic prediction, risk assessment, and decision analysis.

STEP Biosketch:

I study climate change and decision making under uncertainty. My research interests encompass a broad range of questions related to climate prediction, uncertainty, learning, and economic policy analysis. What is our uncertainty about the future climate, how can we reduce this uncertainty, and what are its policy implications, accounting for our ability to learn over time? What are our practical limitations in how accurately and quickly we can learn about the future?

My work involves many aspects of the Earth system, including climate system feedbacks, nonlinearities, and thresholds ("tipping points"); ice sheet dynamics and sea level rise; shallow and deep time paleoclimate; biogeochemistry and the terrestrial and ocean carbon cycles; and interactions between these systems (e.g., cryosphere-ocean-carbon cycle interactions).

My main methodological approach is Bayesian data-model calibration, which assigns probabilities to climate simulation scenarios in proportion to how well they agree with observed data. I am interested in how to statistically combine diverse lines of evidence and models in order to most effectively use the information contained therein, accounting for inevitable limitations in the quality of both the data and the models.

I am currently working on projects related to learning about climate system feedbacks and ice sheet stability.

Curriculum Vitae

Publications

R. Olson, R. Sriver, M. Goes, N.M. Urban, H.D. Matthews, M. Haran, and K. Keller, A climate sensitivity estimate using Bayesian fusion of instrumental observations and an Earth System model, Journal of Geophysical Research—Atmospheres, in press (2012).
P.J. Applegate, N.M. Urban, K. Keller, T.V. Lowell, B.J.C. Laabs, M.A. Kelly, and R.B. Alley, Improved moraine age interpretations through explicit matching of geomorphic process models to cosmogenic nuclide measurements from single landforms, Quaternary Research, in press (2012).
R.L. Sriver, N.M. Urban, R. Tonkonojenkov, and K. Keller, "Towards a physically plausible upper bound of sea-level projections", in preparation (2011).
C.M. Little, M. Oppenheimer, and N.M. Urban, "A probabilistic, bottom-up approach to ice sheet driven sea level rise projections", in revision (2011).
A. Schmittner, N.M. Urban, J.D. Shakun, N.D. Mahowald, P.U. Clark, P.J. Bartlein, A.C. Mix, and A. Rosell-Melé, Climate sensitivity estimated from temperature reconstructions of the Last Glacial Maximum, Science 334, 1385 (2011). [supplement] [journal]
N.M. Urban, T.J. Bralower, M. Haran, and K. Keller, A statistical interpretation of surface ocean temperature trends during the Paleocene-Eocene Thermal Maximum, Paleoceanography, in review (2011) . [data]
Y. Cui, L.R. Kump, A.J. Ridgwell, A.J. Charles, C.K. Junium, A.F. Diefendorf, K.H. Freeman, N.M. Urban, and I.C. Harding, "Slow release of fossil carbon during the Palaeocene-Eocene Thermal Maximum", Nature Geoscience 4, 481 (2011). [journal]
J. Xiao, K.J. Davis, N.M. Urban, K. Keller, and N. Saliendra, Upscaling carbon fluxes from towers to the regional scale: Influence of parameter variability and land cover representation on regional flux estimates, Journal of Geophysical Research—Biogeosciences, in press (2011). [journal]
M. Haran and N.M. Urban, Discussion of 'A statistical analysis of multiple temperature proxies: are reconstructions of surface temperatures over the last 1000 years reliable?' by McShane and Wyner, Annals of Applied Statistics 5, 61 (2011). [journal]
M. Goes, N.M. Urban, R. Tonkonojenkov, M. Haran, and K. Keller, The skill of different ocean tracers in reducing uncertainties about projections of the Atlantic meridional overturning circulation, Journal of Geophysical Research—Oceans 115, C12006 (2010). [journal]
T.E. Fricker, J.E. Oakley, and N.M. Urban, Multivariate emulators with nonseparable covariance structures, Technometrics, in revision (2011).
D.M. Ricciuto, R. Tonkonojenkov, R.D. Wilkinson, N.M. Urban, D. Matthews, K.J. Davis, and K. Keller, Assimilation of global carbon cycle observations into an Earth system model to estimate uncertain terrestrial carbon cycle parameters, Global Biogeochemical Cycles, in revision (2011).
N.M. Urban and K. Keller, Probabilistic hindcasts and projections of the coupled climate, carbon cycle, and Atlantic meridional overturning circulation systems: A Bayesian fusion of century-scale observations with a simple model, Tellus A 62, 737 (2010). [journal]
P.J. Applegate, N.M. Urban, K. Keller, and R.B. Alley, Modeling the statistical distributions of cosmogenic exposure dates from moraines, Geoscientific Model Development 2, 1407 (2010). [journal]
N.M. Urban and T.E. Fricker, A comparison of Latin hypercube and grid ensemble designs for the multivariate emulation of an Earth system model, Computers & Geosciences 36, 746 (2010). [journal]
A. Schmittner, N.M. Urban, K. Keller, and D. Matthews, Using tracer observations to reduce the uncertainty of ocean diapycnal mixing and climate-carbon cycle projections, Global Biogeochemical Cycles 23, GB4009 (2009). [journal]
N.M. Urban and K. Keller, Complementary observational constraints on climate sensitivity, Geophysical Research Letters 36, L04708 (2009). [journal]
D.E. Shai, N.M. Urban, and M.W. Cole, Structure and heat capacity of Ne and Xe adsorbed on a bundle of carbon nanotubes from Monte Carlo calculations, Physical Review B 77, 205427 (2008). [journal]
N.M. Urban and M.W. Cole, Quantum fluids in nanopores, International Journal of Modern Physics B 20, 5264 (2006). [journal]
N.M. Urban, S.M. Gatica, M.W. Cole, and J.L. Riccardo, Thermodynamic properties and correlation functions of Ar films on the surface of a bundle of nanotubes, Physical Review B 71, 245410 (2005). [journal]