michael e. mann department of meteorology and earth and environmental systems institute (essi) penn...

Michael E. MannDepartment of Meteorology and

Earth and Environmental Systems Institute (ESSI)

Penn State University

National Academy of SciencesMarch 3, 2006

Climate Over the Past 1-2 Millennia

INSTRUMENTAL TEMPERATURE

RECORD

GLOBAL PROXY

CLIMATE RECORDS

Annual Resolution Proxy Climate Indicators

Reconstructed Surface Temperatures

Mann, M.E., Bradley, R.S., Hughes, M.K., Global-Scale Temperature Patterns and Climate Forcing Over the

Past Six Centuries, Nature, 392, 779-787, 1998.


Climate Change 2001: The Scientific Basis, Houghton, J.T.,

et al. (eds.), Cambridge Univ. Press, Cambridge, 2001


Climate Change 2001: The Scientific Basis, Houghton, J.T., et al. (eds.), Cambridge Univ. Press, Cambridge, 2001

Jones, P.D., Mann, M.E., Climate Over Past Millennia, Reviews of Geophysics, 42, RG2002, doi:10.1029/2003RG000143, 2004.


Reconstructions of Northern Hemisphere mean temperatures for the last 1000 years and instrumental record (black line)

From “Wikipedia”

Oerlemans, J., Extracting a climate signal from 169 Glacier Records, Science, March 3 (2005).

From “Wikipedia”

Oerlemans (2005) Glacier-based estimate

Natural

1000 1200 1400 1600 1800 2000

Volcanism

Solar

CLIMATE FORCINGS

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

CLIMATE FORCINGS

Anthropogenic

Greenhouse Gases

Industrial Aerosols

Climate Change 2001: The Scientific Basis, Houghton, J.T.,

et al. (eds.), Cambridge Univ. Press, Cambridge, 2001


MODEL SIMULATIONS

Past CO2 as an additional constraint?

Gerber, S., Joos, F., Bruegger, P.P., Stocker, T.F. Mann, M.E., Sitch, S., Scholze, M., Constraining temperature variations over the last millennium by comparing simulated and observed atmospheric CO2, Climate Dynamics, in press (2002)

Gerber, S., Joos, F., Bruegger, P.P., Stocker, T.F. Mann, M.E., Sitch, S., Scholze, M., Constraining temperature variations over the last millennium by comparing simulated and observed atmospheric CO2, Climate Dynamics, in press (2002)

Model forced by long-term natural and anthropogenic radiative forcing

Sensitivity varied from 1.5 to 4.5oC/2xCO2 (orange shading)Esper et al recon. well

outside range…

Mann et al

Bern “CC” Climate Model


Gerber, S., Joos, F., Bruegger, P.P., Stocker, T.F. Mann, M.E., Sitch, S., Scholze, M., Constraining temperature variations over the last millennium by comparing simulated and observed atmospheric CO2, Climate Dynamics, , 20, 281-299, 2003.

Mann et al


Bern “CC” (coupled Climate Carbon cycle) model includes Lund-Potsdam-Jena Dynamic Global Vegetation Model w/ Impulse Response Representation of Ocean Dynamics

Allows prediction of natural variations in CO2

as a response to large-scale surface temperature changes


Model forced by long-term natural and anthropogenic radiative forcing

Sensitivity varied from 1.5 to 4.5oC/2xCO2 (orange shading)

Mann et al



Natural CO2 variations from Ice Cores consistent with the model predictions for the moderate sensitivities consistent w/ Mann et al reconstruction

Gerber, S., Joos, F., Bruegger, P.P., Stocker, T.F. Mann, M.E., Sitch, S., Scholze, M., Constraining temperature variations over the last millennium by comparing simulated and observed atmospheric CO2, Climate Dynamics, , 20, 281-299, 2003.

Natural CO2 variations from Ice Cores consistent with the model predictions for the moderate sensitivities consistent w/ Mann et al reconstruction

Larger temperature variations (e.g., greater sensitivity of temperature to solar variability) is inconsistent with comparison of modeled and observed CO2



Mann, M.E., Bradley, R.S., Hughes, M.K., GRL, ‘99

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

EUGENE R. WAHL1 and CASPAR M. AMMANN2

1 Environmental Studies and Geology Division, Alfred University, Alfred, New York, U.S.A. One Saxon Dr., Alfred, NY 14802 [email protected] 607.871.2604 607.871.2697 (fax)

2 National Center for Atmospheric Research[1], Boulder, Colorado, U.S.A.The authors contributed equally to the development of the research presented.

(Climatic Change, in press)

Abstract. The Mann et al. (1998) Northern Hemisphere annual temperature reconstruction over 1400-1980 is examined in light of recent criticisms concerning the nature and processing of included climate proxy data. A systematic sequence of analyses is presented that examine issues concerning the proxy evidence, utilizing both indirect analyses via exclusion of proxies and processing steps subject to criticism, and direct analyses of principal component (PC) processing methods in question. Altogether new reconstructions over 1400-1980 are developed in both the indirect and direct analyses, which demonstrate that the Mann et al. reconstruction is robust against the proxy-based criticisms addressed. In particular, reconstructed hemispheric temperatures are demonstrated to be largely unaffected by the use or non-use of PCs to summarize proxy evidence from the data-rich North American region. When proxy PCs are employed, neither the time period used to "center" the data before PC calculation nor the way the PC calculations are performed significantly affects the results, as long as the full extent of the climate information actually in the proxy data is represented by the PC time series. Clear convergence of the resulting climate reconstructions is a strong indicator for achieving this criterion. Also, recent "corrections" to the Mann et al. reconstruction that suggest 15th century temperatures could have been as high as those of the late-20th century are shown to be without statistical and climatological merit. Our examination does suggest that a slight modification to the original Mann et al. reconstruction is justifiable for the first half of the 15th century (~ +0.05°), which leaves entirely unaltered the primary conclusion of Mann et al. (as well as many other reconstructions) that both the 20th century upward trend and high late-20th century hemispheric surface temperatures are anomalous over at least the last 600 years. Our results are also used to evaluate the separate criticism of reduced amplitude in the Mann et al. reconstructions over significant portions of 1400-1900, in relation to some other climate reconstructions and model-based examinations. We find that, from the perspective of the proxy data themselves, such losses probably exist, but they may be smaller than those reported in other recent work.

MBH98 readily reproduced in independent analysis, when the full data set and correct method are folllowed.

Putative reconstruction indicating anomalous 15th century warmth results from censoring of key tree-ring data, and not any purported

‘errors’ in MBH98.

This reconstruction dramatically fails verification.

The MBH98 Reconstruction is largely insensitive to whether PCA is used to represent tree-ring networks.

The MBH98 Reconstruction is largely insensitive to the centering convention used in PCA to represent tree-ring networks, as long as

standard selection rules are followed.

Putative anomalous 15th century warmth follows from exclusion of key data. The resulting reconstructions fail verification.

Failure to reject reconstructions which fail statistical verification also invalidates conclusions of Von Storch et

al (2004) and Burger and Cubasch (2005).

Putative anomalous 15th century warmth follows from exclusion of key data. The resulting reconstructions fail verification.

RegEM Approach vs MBH98 PCA approach

“CFR” approaches

Rutherford, S., Mann, M.E., Osborn, T.J., Bradley, R.S., Briffa, K.R., Hughes, M.K., Jones, P.D., Proxy-based Northern Hemisphere Surface Temperature Reconstructions: Sensitivity to Methodology, Predictor network, Journal of Climate, 18, 2308-2329, 2005.

RegEm Approach vs MBH98 PCA approach



composite of 8 NH proxy series (Mann and Jones ’03)

Composite of 7 NH proxy series (North American PC#1 tree-ring series eliminated)

Instrumental NH Series

RegEm Approach vs MBH98 PCA approach



Geophysical Research Letters, 29 (10), 1501, doi: 10.1029/2001GL014554, 2002.


1877

Journal of Climate, 16, 462-479, 2003

85% missing

95% missing

Pseudo-Proxy Model Reconstruction

von Storch et al. 2004

poorcalibration

and verification

MBH98 and other CFR Methodsguards against

this!

Burger and Cubasch

(2005) suffers from

same problem.

“CFR” approach

Mann, M.E., Rutherford, S., Wahl, E., Ammann, C., Testing the Fidelity of Methods Used in Proxy-based Reconstructions of Past Climate, Journal of Climate, 18, 4097-4107, 2005.

“CFR” approach

Mann, M.E., Rutherford, S., Wahl, E., Ammann, C., Testing the Fidelity of Methods Used in Proxy-based Reconstructions of Past Climate, Journal of Climate, 18, 4097-4107, 2005.

“CFR” approach

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.

“Maunder Minimum”

Influence of Natural Radiative Forcing

LIA winter cooling in Europe associated with

an NAO trend due to solar irradiance changes,

interacting w/ stratospheric

atmospheric dynamics and chemistry

Empirical

NASA/GISS Model

European Winter Cooling During the Little Ice Age

Shindell, D.T., Schmidt, G.A., Mann, M.E., Rind, D., Waple, A., Solar forcing of regional climate

change during the Maunder Minimum, Science, 294, 2149-

2152, 2001.

Shindell, D.T., Schmidt, G.A., Miller, R., Mann, M.E., Volcanic and Solar forcing of Climate Change During the Pre-Industrial era, Journal of Climate, 16, 4094-4107, 2003.

Volcanic Radiative Summer Cooling

Ensemble average summer (Jun-Aug) surface temperature response following eruption of Pinatubo.

Volcanic Winter Dynamical Warming

Ensemble average winter (Dec-Feb) surface temperature response following eruption of Pinatubo.


Esper, J., Cook, E.R., Schweingruber, F.H., Low-Frequency Signals in Long Tree-Ring Chronologies for Reconstructing Past Temperature Variability, Science, 295, 2250-2253, 2002.

Mid-Latitude SummersGreater variability?

Mid-Latitude Summers

1000 1200 1400 1600 1800 2000

Greater variability?

Proxy basedreconstruction

GCM Solar + Volcanic patterns

Annual averagelate 17th vs late 18th Century Temperature change


1998 Global Temperature Pattern

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)


Tropical Volcanic radiative forcing (0.1 x W/m2)



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 The Tropical Pacific Over the Past 1000 Years, Journal of Climate, 18, 447-456, 2005.

Tropical volcanic radiative forcing (0.1 x W/m2)


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 the Tropical Pacific Over the Past 1000 Years, Journal of Climate, 18, 447-456, 2005.

Tropical volcanic radiative forcing (0.1 x W/m2)



40 year smooth

Tropical Solar radiative forcing (W/m2)



Response to Solar Forcing

40 year smooth

Tropical Solar radiative forcing (W/m2) (40 year smooth)



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)


El Nino and North American Drought

El Nino vs. North American Drought over the Past Century

Increased Drought La Nina

El NinoLess Drought

Courtesy of E.Cook

Linear correlation

coefficient (r) is not a viable

measure of statistical

reconstruction skill

michael e. mann department of meteorology and earth and environmental systems institute (essi) penn...

Documents

climate dynamics

climate signal

bern cc climate model

wikipedia slide

bern cc climate model

climate carbon cycle

orange shading slide

past millennia