Volcanic and Solar Forcing of El Nino over the Past 1000 Years

Department of Environmental Sciences, University of Virginia, Charlottesville, VA

European Geophysical UnionNice, FranceApril 27, 2004

Michael E. Mann

Mark A. CaneLamont Doherty Earth Observatory, Columbia University, New York, NY

Stephen E. ZebiakInternational Research Institute For Climate Prediction, Palisades, NY

Amy ClementRosensteil School of Oceanography, University of Miami, Miami, FL

Influence of Natural Radiative Forcing

1000 1200 1400 1600 1800 2000

Volcanism

Solar

Crowley, T.J., Causes of Climate Change Over the Past 1000 Years, Science, 289 270-277, 2000.

Jones, P.D., Mann, M.E., Climate Over Past Millennia, Reviews of Geophysics, in press, 2004.

Adams, J.B., Mann, M.E., Ammann, C.M., Proxy evidence for an El Nino-like Response to Volcanic Forcing, Nature, 426, 274-278, 2003.

Volcanic Forcing of El Nino?

Adams, J.B., Mann, M.E., Ammann, C.M., Proxy evidence for an El Nino-like Response to Volcanic Forcing, Nature, 426, 274-278, 2003.

Volcanic Forcing of El Nino?

Decadally-smoothed Mann et al NINO3 (x-1)

Jones et al, Science, 2001

Solar Forcing of El Nino?

Verschuren et al, Nature, 403, 410-414, 2000.

Cane, M.A., A.C. Clement, A. Kaplan, Y. Kushnir, D. Pozdnyakov, R. Seager, S.E. Zebiak, and R. Murtugudde, Twentieth-Century Sea Surface Temperature Trends, Science, 275, 957-960, 1997.

Theoretical mechanism for natural radiative forcing of El Nino

Composite Nino3 (100 realizations of CZ model)

Theoretical mechanism for natural radiative forcing of El Nino

Tropical Volcanic radiative forcing (0.1 x W/m2)

Composite Nino3 (100 realizations of CZ model)

Theoretical mechanism for natural radiative forcing of El Nino

Response to Volcanic Forcing

Tropical Volcanic radiative forcing (0.1 x W/m2)

Mann, M.E., Cane, M.A., Zebiak, S.E., Clement, A., Volcanic and Solar Forcing of El Niño Over the Past 1000 Years, submitted, 2004.

Tropical volcanic radiative forcing (0.1 x W/m2)

Theoretical mechanism for natural radiative forcing of El Nino

Superposed Epoch Analysis AD 1649-1868

all (7) tropical events exceeding -2 W/m2

Superposed Epoch Analysis AD 1000-1999

All (7) tropical events exceeding -4 W/m2

Mann, M.E., Cane, M.A., Zebiak, S.E., Clement, A., Volcanic and Solar Forcing of El Niño Over the Past 1000 Years, submitted, 2004.

Tropical volcanic radiative forcing (0.1 x W/m2)

Composite Nino3 (100 realizations of CZ model)

Theoretical mechanism for natural radiative forcing of El Nino

40 year smooth

Tropical Solar radiative forcing (W/m2)

Composite Nino3 (100 realizations of CZ model)

Theoretical mechanism for natural radiative forcing of El Nino

Response to Solar Forcing

40 year smooth

40 year smooth

Tropical Solar radiative forcing (W/m2)

Mann, M.E., Cane, M.A., Zebiak, S.E., Clement, A., Volcanic and Solar Forcing of El Niño Over the Past 1000 Years, submitted, 2004.

Theoretical mechanism for natural radiative forcing of El Nino

Cobb, K.M., C.D. Charles, R.L Edwards, H. Cheng, El Niño-Southern Oscillation and tropical Pacific climate during the last millennium, Nature, 424, 271-276, 2003.

Theoretical mechanism for natural radiative forcing of El Nino

Combined response to Solar +Volcanic Forcing

Ensemble mean Nino3 (100 realizations of CZ model)

40 year smooth

Palymra coral isotopes (standardized to have same mean and standard deviation as Nino3 composite series)

Mann, M.E., Cane, M.A., Zebiak, S.E., Clement, A., Volcanic and Solar Forcing of El Niño Over the Past 1000 Years, submitted, 2004.

Mann, M.E., Ammann, C., Bradley, R.S., Briffa, K., Crowley, T.J., Hughes, M.K., Jones, P.D., Oppenheimer, M., Osborn, T.J., Overpeck, J.T., Rutherford, S., Trenberth, K.E., Wigley, T.M.L., On Past Temperatures and Anomalous late 20th Century Warmth, Eos, 84, 256-258, 2003 [MODIFIED: Boreholes—Rutherford and Mann (in press); Crowley & Lowery (updated)]

Mann, M.E., Ammann, C., Bradley, R.S., Briffa, K., Crowley, T.J., Hughes, M.K., Jones, P.D., Oppenheimer, M., Osborn, T.J., Overpeck, J.T., Rutherford, S., Trenberth, K.E., Wigley, T.M.L., On Past Temperatures and Anomalous late 20th Century Warmth, Eos, 84, 256-258, 2003 [MODIFIED: Boreholes—Rutherford and Mann (in press); Crowley & Lowery (updated)]

Greater variability in extratropics and

summer!

CONCLUSIONS•Observations of an El Nino-like response to explosive tropical volcanic eruptions are consistent with results based on simulations with the Cane-Zebiak model

•Coral evidence of La Nina-like anomalies during the 12th-early 13th centuries, and El Nino-like anomalies during the late 17th century, are reproduced by the simulated response to total (solar+volcanic) natural radiative forcing

•Differences between empirical estimates of extratropical and full (combined tropical and extratropical) hemispheric mean temperature changes in past centuries may reflect the importance of tropical dynamical responses.

Jones, P.D., Mann, M.E., Climate Over Past Millennia, Reviews of Geophysics, in press, 2004.