Variability in El Nino and the Global ENSO phenomenon

in past centuries

Michael E. MannDepartment of Environmental Sciences

University of Virginia

Global Change Open Science Conference

Amsterdam, The NetherlandsWednesday, 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, 357-412, 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, 91-101, 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, 2001.

RELATED PUBLICATIONS

http://www.people.virginia.edu/~mem6u/research.html

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 (1902-1980)

Verification (1854-1901)

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 (1902-1980)

= 0.49 (Nino3)

Verification (1865-1901)

r2 = 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 1661. 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, 853-871, 2001)

Regularized Expectation Maximization (“RegEM”)

Algorithm

submitted

Training Interval

Reconstruction Interval

NINO3 INDEX

Madison Weather Diaries

Madison’s 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 12th, 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