Variability in El Nino and the Global ENSO phenomenon in past centuries Michael E. Mann Department of Environmental Sciences University of Virginia Global Change Open Science Conference Amsterdam, The Netherlands Wednesday, July 11, 2001 CO-INVESTIGATORS & COLLABORATORS R. Bradley M. Hughes S. Rutherford T. Delworth R. Stouffer D. Druckenbrod D. Stahle Mann, M.E., Bradley, R.S., Hughes, M.K., Long-term variability in the El Nino Southern Oscillation and associated teleconnections, Diaz, H.F. & Markgraf, V. (eds) El Nino and the Southern Oscillation: Multiscale Variability and its Impacts on Natural Ecosystems and Society, Cambridge University Press, Cambridge, UK, , 2000a. Bradley, R.S., Mann, M.E., Gille, E., Bradley, R.S., Hughes, M.K., Overpeck, J.T., Keimig, F.T., Gross, W., Global Temperature Patterns in Past Centuries: An interactive presentation, Earth Interactions, 4-4, 1-29, 2000b. Mann, M.E., Climate During the Past Millennium, Weather (invited contribution), 56, , 2001a. Mann, M.E., Large-scale Temperature Patterns in Past Centuries: Implications for North American Climate Change, Human and Ecological Risk Assessment, accepted, 2001c. Rutherford, S., Mann, M.E., Delworth, T.L., Stouffer, R., The Performance of Covariance-Based Methods of Climate Field Reconstruction Under Stationary and Nonstationary Forcing, J. Climate, in review, RELATED PUBLICATIONS OVERVIEW Background Influence of non-stationarity? Historical Information Conclusions Background INSTRUMENTAL TEMPERATURE RECORD GLOBAL PROXY CLIMATE RECORDS Five leading patterns of global temperature variation during the 20th century. Reconstructions of time histories of 5 leading temperature patterns. Note that fewer eigenvectors are reconstructed further back in time. 1791 RECONSTRUCTED GLOBAL TEMPERATURE PATTERNS Calibration ( ) Verification ( ) Northern Hemisphere Mean Temperature EL NINO/SOUTHERN OSCILLATION (ENSO) Multivariate ENSO Index (MEI) Substantial interannual climate variability associated with ENSO, but decadal variability is also evident as well. The recent decadal trend towards El Nino conditions could be natural or anthropogenic. Calibration ( ) = 0.49 (Nino3) Verification ( ) r 2 = 0.52 (SOI) Cold-season Nino3 Pacific Decadal Oscillation?? Decadal ENSO-like variability Biondi, F., Gershunov, A. & Cayan, D. R. North Pacific Decadal Climate Variability since Journal of Climate 14, 5-10 (2001). PDO?? Sensitivity to Non-Stationarity? Alternative Statistical Approach: (T. Schneider, Analysis of Incomplete Climate Data: Estimation of Mean Values and Covariance Matrices and Imputation of Missing Values, J. Climate, 14, , 2001) Regularized Expectation Maximization (RegEM) Algorithm submitted Training Interval Reconstruction Interval NINO3 INDEX Madison Weather Diaries Madisons interest in natural science arose from conversations with his close friend and neighbor, Thomas Jefferson (Cohen 1995). In fact, as recorded in a letter dated March 16, 1784, James Madison initially began this journal at the urging of Jefferson, who wrote: I wish you would keep a diary under the following heads or columns: 1. day of the month 2. thermometer at sunrise. 3. barometer at sunrise. 6. thermometer at 4. P. M. 7. barometer at 4. P. M. 4 direction of wind at sunrise. 8. direction of wind at 4. P. M. 5. the weather viz rain, snow, fair at sunrise &c. 9. weather at 4. P. M. 10. shooting or falling of the leaves of trees, of flours, & other remarkable plants. 11. appearance or disappearance of birds, their emigrations &c. 12. Miscellanea. It will be an amusement to you & may become useful. (footnote explaining mis-ordering of columns: The above columns to be arranged according to the order of the numbers as corrected. When Madison returned to Montpelier from the first session of the Second Congress in Philadelphia, he wrote in a letter to Jefferson dated June 12 th, 1792: I found this Country labouring under a most severe drought. There had been no rain whatever since the 18 or 20 of April. The flax and oats generally destroyed; The corn dying in the hills, no tobacco planted, and the wheat in weak land suffering; in the strong, not injured materially; in the very strong perhaps benefited. (letter goes on to say that more, and heavy rain came in June). Verif: r=0.45; Calib: r=0.52 WINTER 1791/1792 CONCLUSIONS Proxy-based reconstructions of ENSO provide reasonably reliable chronology El Nino and decadal ENSO-like variability over past few centuries and Influence of non-stationarity does not appear to be problematic Prospects for enhanced ENSO-sensitive data; improved reconstructions