I am an Energy Security Fellow in the Computational Physics and
Methods group (CCS-2) at Los Alamos National Laboratory.
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.
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
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, ice sheet stability, and ocean data assimilation (regional-decadal climate forecasting).
- J. Xiao, K.J. Davis, N.M. Urban, and K. Keller, "Uncertainty in model parameters and regional carbon fluxes: A model-data fusion approach", Global Change Biology, in review (2013).
- M. Escarra, L.T. Le, N.M. Urban, M. Oppenheimer, and C.F. Gmachl, "Quantum cascade laser-based sensing for carbon sequestration leakage monitoring", IEEE Sensors Journal, in press (2013). [journal]
- R. Olson, R. Sriver, W. Chang, M. Haran, N.M. Urban, and K. Keller, "What is the effect of unresolved internal climate variability on climate sensitivity estimates?", Journal of Geophysical Research—Atmospheres, in press (2013).
- C.M. Little, M. Oppenheimer, and N.M. Urban, "Upper bounds on twenty-first-century Antarctic ice loss assessed using a probabilistic framework", Nature Climate Change, in press (2013).
- C.M. Little, N.M. Urban, and M. Oppenheimer, "Probabilistic framework for assessing the ice sheet contribution to sea level change", Proceedings of the National Academy of Sciences 110, 3264
- T.E. Fricker, J.E. Oakley, and N.M. Urban, Multivariate emulators with nonseparable covariance structures, Technometrics 55, 47 (2013). [journal]
- T.W. Hilton, K.J. Davis, K. Keller, and N.M. Urban, "Improving terrestrial CO2 flux diagnosis using spatial structure in land surface model residuals", Biogeosciences Discussions, 9, 7073 (2013), in revision. [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 revision (2011). [data]
- R.L. Sriver, N.M. Urban, R. Olson, and K. Keller, "Toward a physically plausible upper bound of sea-level rise projections", Climatic Change 115, 893 (2012). [journal]
- 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 117, D04103 (2012). [journal]
- 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 77, 293 (2012). [journal]
- 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]
- 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,
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 116, G00J06 (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]
- 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 (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]