Caspar M. Ammann

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Dr. Ammann is a Project Scientist III working in the Climate Science and Applications Program (CSAP) at the National Center for Atmospheric Research in Boulder, Colorado. Ammann has a doctorate in geosciences from the University of Massachusetts, and a master’s degree in geography, geology and mineralogy from the University of Bern, Switzerland. He is studying global and regional climate, how and why it varies naturally, and how recent changes in human activity (emissions, landuse changes) already have and might further alter the climate across time and space. His efforts support science applications that advance the use of predictions and projections for the provision of useful and usable information through standardize methods and tools. Such high resolution climate information can inform and facilitate decision making and planning. Dr. Ammann has also been involved in the IGBP-PAGES project focusing on regional climate dynamics of the past 2,000 years and the PAGES-CLIVAR Paleoclimate Reconstruction Challenge. He also has been as a member of the Scientific Advisiory Committee for NASA-Living with a Star, TR&T program, and served on a National Research Council evaluation panel on detection and attribution of solar effect on climate. He was a member of numerous scientific organizing committees for national and international conferences and meetings in the field of climate and statistical climatology. Most recently, he got elected to Chair the Scientific Steering of SEARCH (Study of Environmental Arctic Change), an interdiscplinary Arctic program with the mission to provide a foundation to Arctic change science through collaboration with the research community, funding agecies, and other stakeholders.


Climate change ...


Understanding how climate reconstructions ...

More information is available at the PR-Challenge Site

North American Forced Climate Change in the Past

Regional Climate ...


  • Graham N.E., C.M. Ammann, D. Fleitmann, K.M. Cobb, and J. Luterbacher, 2011: Support for a Global Climate Reorganization during the “Medieval Climate Anomaly”. Clim. Dyn., 10.1007/s00382-010-0914-z.
  • Wahl E.R., and C.M. Ammann, 2011: Discussion of: A statistical analysis of multiple temperature proxies: Are re- constructions of surface temperatures over the last 1000 years reliable? The Annals of Applied Statistics, 5(1), 91-95. doi: 10.1214/10-AOAS398J.



  • Ammann C.M., W.M. Washington, G. Meehl, L. Buja, and H. Teng, 2010: Climate Engineering through artificial enhancement of natural forcings: Magnitudes and implied consequences. J. Geophys. Res., 115, D22109, doi:10.1029/2009JD012878.
  • Li B., D. W. Nychka, and C.M. Ammann, 2010: The Value of Multi-proxy Reconstruction of Past Climate. The Journal of American Statistical Association, Applications and Case Studies, 105, 491, 883-900. doi: 10.1198/jasa.2010.ap09379.Ammann C.M., M.G. Genton, and B. Li, 2010: Technical Note: Correcting for signal attenuation from noisy proxy data in climate reconstructions. Climate of the Past, 6, 273-279.
  • Anchukaitis K. J., B. M. Buckley, E. R. Cook, B. I. Cook, R. D. D’Arrigo, and C. M. Ammann, 2010: The influence of volcanic eruptions on the climate of the Asian monsoon region. Geophys. Res. Lett., L22703, doi: 2010GL044843R.
  • Schmidt, G. A., Jungclaus, J. H., Ammann, C. M., Bard, E., Braconnot, P., Crowley, T. J., Delaygue, G., Joos, F., Krivova, N. A., Muscheler, R., Otto-Bliesner, B. L., Pongratz, J., Shindell, D. T., Solanki, S. K., Steinhilber, F., and Vieira, L. E. A.: Climate forcing reconstructions for use in PMIP simulations of the last millennium (v1.0), Geosci. Model Dev. Discuss., 3, 1549-1586, doi:10.5194/gmdd-3-1549-2010, 2010.
  • Ammann C.M., and P. Naveau, 2010: A statistical volcanic forcing-scenario generator for climate simulations. J. Geophys. Res., doi:10.1029/2009JD012550.
  • Rutherford S.D, M.E. Mann, C.M. Ammann, E.R. Wahl, 2010: Comment on “A surrogate ensemble study of climate reconstruction methods: Stochasticity and robustness” by Christiansen, Schmith and Thejll, J. of Climate.



  • Kaufman D.S., D.P. Schneider, N.P. McKay, C.M. Ammann, R.S. Bradley, K.R. Briffa, G.H. Miller, B.L. Otto-Bliesner, J.T. Overpeck, B.M. Vinther, Arctic Lakes 2k Project Members, 2009: Recent warming reverses long-term Arctic cooling. Science, 325, 1236, doi:10.1126/science.1173983.
  • Mann M.E., Z. Zhang, S. Rutherford, R.S. Bradley, M.K. Hughes, D. Shindell, C.M. Ammann, G. Faluvegi, and F. Ni, 2009: Global Signatures and Dynamical Origins of the Little Ice Age and Medieval Climate Anomaly. Science, 326, 1256-1260. doi:10.1126/science.1177303.
  • Schneider D.P., C.M. Ammann, B.L. Otto-Bliesner, and D.S. Kaufman, in press: Climate response to large, high-latitude and low-latitude volcanic eruptions in the Community Climate System Model. J. Geophys. Res.
  • Hughes, M.K., and Ammann C.M., 2009: The Future of the Past: An Earth System Framework for high resolution paleoclimatology: Editorial Essay. Clim. Change 10.1007/s10584-009-9588-0.
  • Fan F., M.E. Mann, and C.M. Ammann, 2009: Understanding Changes in the Asian Summer Monsoon over the Past Millennium. J. Climate, 22(7), 1736–1748. DOI: 10.1175/2008JCLI2336.1.



  • Gao, C., A. Robock, and C. Ammann, 2008: Volcanic forcing of climate over the past 1500 years: An improved ice core-based index for climate models, J. Geophys. Res., 113, D23111, doi:10.1029/2008JD010239.
  • P.D. Jones, K.R. Briffa, T.J. Osborn, J. M. Lough, T.D. van Ommen, B. Vinther, J. Luterbacher, E.R. Wahl. F.W. Zwiers, M.E. Mann, G.A. Schmidt, C.M. Ammann, B.M. Buckley, K.M. Cobb, J. Esper, H. Goosse, N. Graham, E. Jansen, T. Kiefer, C. Kull, M. Kuettel, E. Mosley-Thompson, J.T .Overpeck, N. Riedwyl, M. Schulz, A.W. Tudhope, R. Villalba, H. Wanner, E. Wolff and E. Xoplaki, 2009: High-resolution paleoclimatology of the last millennium: a review of current status and future prospects. The Holocene, 19, 3-50.
  • Robock A., C.M. Ammann, L. Oman, D. Shindell, and G. Stenchikov, 2009: Did the Toba volcanic eruption of ~74k BP produce an ice age? J. Geophys. Res., 114, doi:10.1029/2008JD011652, 2009.
  • Rutherford S., M.E. Mann, E.R. Wahl, and C.M. Ammann, 2008: Reply to: Comment by Jason E. Smerdon on ‘Robustness of proxy-based climate field reconstruction methods’. J. Geophys. Res., 113, D18107, doi:10.1029/2008JD009964, 2008.
  • Gao, C., A. Robock, and C. Ammann, 2008: Volcanic forcing of climate over the past 1500 years: An improved ice core-based index for climate models, J. Geophys. Res., 113, D23111, doi:10.1029/2008JD010239.



  • Ammann C.M., F. Joos, D. Schimel, B.L. Otto-Bliesner, and R. Tomas, 2007: Solar influence on climate during the past millennium: results from transient simulations with the NCAR Climate System Model. Proc. Nat. Acad. Sci. 104(10), 3713-3718.
  • Li B., D. Nychka and C.M. Ammann, 2007: The “Hockey Stick” and the 1990s: A statistical perspective on reconstructing hemispheric temperatures. Tellus, doi:10.111/j.1600-0870.2007.00270.x.
  • Ammann C.M., and E.R. Wahl, 2007: Importance of the Geophysical Context for Statistical Evaluation of Climate Reconstruction Procedures. Climatic Change, doi:10.1007/s10584-007-9276-x.
  • Wahl, E.R and C.M. Ammann, 2007: Robustness of the Mann, Bradley, Hughes reconstruction of Northern Hemisphere surface temperatures: Examination of criticisms based on the nature and processing of proxy climate evidence. Climatic Change, doi:10.1007/s10584-006-9105-7.
  • Mann M.E., S. Rutherford, E. Wahl, and C.M. Ammann, 2007: Reply to comment on “Testing the Fidelity of Methods used in Proxy-Based Reconstructions of Past Climate” by Zorita E., F. Gonzalez-Rouco, and H. von Storch, J. Climate, 20, 3699-3703, doi: 10.1175/JCLI4172.1
  • Mann M.E., S. Rutherford, E. Wahl, C.M. Ammann, 2007: Reply to “Comments on ‘Testing the fidelity of methods used in proxy-based reconstructions of past climate’: The role of standardization interval.” By J. Smedon and A. Kaplan. J. Climate, 20, 5671-5674.
  • Graham N.E., M.R. Hughes, C.M. Ammann, K.M. Cobb, M.P. Hoerling, D.J. Kennett, J.P. Kennett, B. Rein, L. Stott, P.E. Wigand, and T. Xu, 2007: Tropical Pacific ‚Äì Mid-Latitude Teleconnections in Medieval Times. Climatic Change. doi:10.1007/s10584-007-9239-2.
  • Mann M.E., S. Rutherford, E. Wahl, and C. Ammann, 2007: Robustness of proxy-based climate field reconstruction methods. J. Geophys. Res., 112, doi:10.1029/2006JD008272, 2007.



  • Gao C., A. Robock, S. Self, J. B. Witter, J. P. Steffenson, H. B. Clausen, M.-L. Siggaard-Andersen, S. Johnsen, P. A. Mayewski, C. Ammann, 2006: The 1452 or 1453 A.D. Kuwae eruption signal derived from multiple ice core records: Greatest volcanic sulfate event of the past 700 years. J. Geophys. Res., 111, D12107, doi:10.1029/2005JD006710.
  • Wahl E.R, D. Ritson, C.M. Ammann, 2006: Comment on “Reconstructing Past Climate from Noisy Data”. Science, doi: 10.1126/science.1120866, 2006.
  • Otto-Bliesner B.L., R. Tomas, E.C. Brady, C.M. Ammann, Z. Kothavala, and G. Clauzet, 2006: Climate sensitivity of moderate- and low-resolution versions of CCSM3 to preindustrial forcings. J. Climate, 19(11), 2567-2583.



  • Mann M.E., S. Rutherford, E.R. Wahl, and C.M. Ammann, 2005: Testing the fidelity of methodologies used in ‘proxy’-based reconstructions of past climate. J. Climate-Letter, 18, 4097-4107.
  • Wigley T.M.L., C.M. Ammann, B.D. Santer, K.E. Ttaylor, 2005: Comment on “Climate forcing by the volcanic eruption of Mount Pinatubo” by David H. Douglass and Robert S. Knox, Geophys. Res. Lett., 32, L20709, doi:10.1029/2005GL023312.
  • Naveau P., M. Nogaj, C.M. Ammann, D. Cooley, V. Jomelli, 2005: Statistical methods for the analysis of geophysical extreme events. Comptes Rendu Geoscience, 337 (10-11), 1013-1022.
  • Goosse H., T.J. Crowley, E. Zorita, C.M. Ammann, H. Renssen, E. Driesschaert, 2005: Modeling the climate of the last millennium: What causes the differences between simulations? Geophys. Res. Lett., 32, L06710, doi:10.1029/2005GL022368.
  • Naveau P. and C.M. Ammann, 2005: Statistical distribution of ice core sulfate from climatically relevant volcanic eruptions. Geophys. Res. Lett., 32, L05711, doi:10.1029/2004GL021732, 2005.
  • Wigley T.M.L., C.M. Ammann, B.D. Santer, and S.C.B. Raper, 2005: Effect of climate sensitivity on the response to volcanic forcing. J. of Geophys. Res., 110, D09107, doi:10.1029/2004JD005557.



  • Santer B.D., T.M.L. Wigley, A.J. Simmons, P.W. Kallberg, G.A. Kelly, S.M. uppala, C.M. Ammann, J.S. Boyle, W.Brueggemann, C. Doutriaux, M. Fiorino, C. Mears, G.A. Meehl, R. Sausen, K.E. Taylor, W.M. Washington, M.F. Wehner, F.J. Wentz, 2004: Identification of Anthropogenic Climate Change using a second-generation Reanalysis. J. Geophys. Res., 109, D21104, doi:10.1029/2004JD005075.
  • Naveau, P., Genton, M. G. and Ammann, C. (2004), "Time series analysis with a skewed Kalman filter," in Skew-Elliptical Distributions and Their Applications: A Journey Beyond Normality, Genton, M. G., Ed., Chapman & Hall / CRC, Boca Raton, FL, pp. 259-278.
  • Meehl, G.A., W.M. Washington, C.M. Ammann, J.M. Arblaster, T.M.L. Wigley, and C. Tebaldi, 2004: Combinations of natural and anthropogenic forcings and 20th century climate. J. Climate, 17, 3721-3727.
  • Adams J.B., M.E. Mann, C.M. Ammann, 2003: Proxy evidence for an El Niño-like response to volcanic forcing. Nature 426, 274-278.


2003 and earlier

  • Mann, M.E., C.M. Ammann, R.S. Bradley, K. Briffa, T.J. Crowley, M. Huges, P.D. Jones, M. Oppenheimer, , T. Osborn, J.T. Overpeck, S. Rutherford, K.E. Trenberth, and T.M.L. Wigley, 2003: On past temperatures and anomalous late 20th century warmth. EOS, 84(27), 256ff.
  • Ammann C.M., G.A. Meehl G., W.M. Washington and C.S. Zender, 2003: A monthly and latitudinally varying volcanic forcing dataset in simulations of the 20th century climate. Geophys. Res. Lett., 30(12), 1657, doi:10.1029/2003GL016875.
  • Santer B.D., M.F. Wehner, T.M.L. Wigley, R. Sausen, G.A. Meehl, K.E. Taylor, C.M. Ammann, J. Arblaster, W.M. Washington, J.S. Boyle, and W. Brueggemann, 2004: Response to comment on “Contributions of anthropogenic and natural forcing to recent tropopause height changes”. Science, 303, 1771.
  • Santer B.D., T.M.L. Wigley, G.A. Meehl, M.F. Wehner, C. Mears, M. Schabel, F.J. Wentz, C.M. Ammann, J. Arblaster, T. Bettge, W.M. Washington, K.E. Taylor, J.S. Boyle, W. Brueggemann, and C. Doutriaux, 2003: Reliability of Satellite Data Sets. Response to comments by Christy and Spencer. Science, 301, 1047-1049.
  • Santer B.D., M.F. Wehner, T.M.L. Wigley, R. Sausen, G.A. Meehl, K.E. Taylor, C.M. Ammann, J. Arblaster, W.M. Washington, J.S. Boyle, W. Brueggemann, 2003: Contributions of anthropogenic and natural forcing to recent tropopause height changes. Science, 301, 479-483.
  • Santer B.D., T.M.L. Wigley, G.A. Meehl, M.F. Wehner, C. Mears, M. Schabel, F.J. Wentz, C.M. Ammann, J. Arblaster, T. Bettge, W.M. Washington, K.E. Taylor, J.S. Boyle, W. Brüggemann, and C. Doutriaux, 2003: Influence of satellite data uncertainties on the detection of externally-forced climate change. Science, 300, 1280-1284.
  • Naveau P., C.M. Ammann, H.S. Oh and W. Guo, 2003: An automatic statistical methodology to extract pulse-like forcing factors in climatic time series: Application to volcanic events. In: Robock, A. and C. Oppenheimer (Eds.): Volcanism and the Earth’s Atmosphere. Geophysical Monograph 139, 177-186, doi: 1029/139GM11.
  • Ammann C.M., P. Naveau, 2003: Multi-decadal periodicity in tropical explosive volcanism and its influence on climate. Geophys. Res. Lett., 30(5), 1210, doi:10.1029/2002GL016388.
  • Oh, H.-S., C.M. Ammann, P. Naveau, D. Nychka, and B.L. Otto-Bliesner, 2003: Multi-resolution time series analysis applied to solar irradiance and climate reconstructions. Journal of Atmospheric and Solar-Terrestrial Physics, 65, 191-201.
  • Ammann C.M., B. Jenny, K. Kammer and B. Messerli, 2001: Late Quaternary Glacier Response to Humidity changes in the Arid Andes of Chile (18°-29°S). Palaeogeography, Palaeoclimatology, Palaeoecology 172, 313-326.
  • Vuille M. and C.M. Ammann, 1997: Regional snowfall patterns in the high, arid Andes. Climatic Change, 36, 413-423.

Caspar M. Ammann
Climate Science and Applications Program
RAL/ National Center for Atmospheric Research
PO Box 3000 Boulder, Colorado USA 80307
Tel: 303-497-1705 Fax: 303-497-8401
Email: ammann at