Transcript Climate over the Past 1-2 Millennia

Climate Over the Past 1-2 Millennia
Michael E. Mann
Department of Meteorology and
Earth and Environmental Systems Institute
(ESSI)
Penn State University
National Academy of Sciences
March 3, 2006
Annual Resolution Proxy Climate Indicators
INSTRUMENTAL
TEMPERATURE
RECORD
GLOBAL
PROXY
CLIMATE
RECORDS
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.
Reconstructed Surface Temperatures
Climate Change 2001: The
Scientific Basis, Houghton, J.T.,
et al. (eds.), Cambridge Univ.
Press, Cambridge, 2001
Reconstructed Surface Temperatures
Climate Change 2001: The Scientific Basis, Houghton, J.T., et
al. (eds.), Cambridge Univ. Press, Cambridge, 2001
Reconstructed Surface Temperatures
Jones, P.D., Mann, M.E., Climate Over Past Millennia, Reviews of Geophysics,
42, RG2002, doi:10.1029/2003RG000143, 2004.
From “Wikipedia”
Reconstructions of Northern Hemisphere mean temperatures
for the last 1000 years and instrumental record (black line)
Oerlemans (2005) Glacierbased estimate
From “Wikipedia”
Oerlemans, J., Extracting a climate signal from 169 Glacier Records,
Science, March 3 (2005).
CLIMATE FORCINGS
Volcanism
1000
1200
1400
1600
1800
Solar
Natural
Crowley, T.J., Causes of
Climate Change Over the
Past 1000 Years, Science,
289 270-277, 2000.
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
Jones, P.D., Mann, M.E., Climate
Over Past Millennia, Reviews of
Geophysics, 42, RG2002,
doi:10.1029/2003RG000143, 2004.
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)
Past CO2 as an additional constraint?
Bern “CC” Climate Model
Model forced by longterm natural and
anthropogenic
radiative forcing
Sensitivity varied from
1.5 to 4.5oC/2xCO2
(orange shading)
Mann et al
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)
Esper et al recon. well
outside range…
Past CO2 as an additional constraint?
Bern “CC” Climate Model
Model forced by longterm natural and
anthropogenic
radiative forcing
Sensitivity varied from
1.5 to 4.5oC/2xCO2
(orange shading)
Mann et al
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.
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
Past CO2 as an additional constraint?
Bern “CC” Climate Model
Mann et al
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
Past CO2 as an additional constraint?
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
Reconstructed Surface Temperatures
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.
“CFR” approaches
RegEM Approach vs MBH98 PCA approach
Rutherford, S., Mann, M.E., Osborn, T.J., Bradley, R.S., Briffa, K.R., Hughes, M.K., Jones, P.D., Proxybased Northern Hemisphere Surface Temperature Reconstructions: Sensitivity to Methodology,
Predictor network, Journal of Climate, 18, 2308-2329, 2005.
“CFR” approaches
RegEm Approach vs MBH98 PCA approach
Rutherford, S., Mann, M.E., Osborn, T.J., Bradley, R.S., Briffa, K.R., Hughes, M.K., Jones, P.D., Proxybased Northern Hemisphere Surface Temperature Reconstructions: Sensitivity to Methodology,
Predictor network, Journal of Climate, 18, 2308-2329, 2005.
Reconstructed Surface Temperatures
Jones, P.D., Mann, M.E., Climate Over Past Millennia, Reviews of Geophysics,
42, RG2002, doi:10.1029/2003RG000143, 2004.
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
“CFR” approaches
RegEm Approach vs MBH98 PCA approach
Rutherford, S., Mann, M.E., Osborn, T.J., Bradley, R.S., Briffa, K.R., Hughes, M.K., Jones, P.D., Proxybased Northern Hemisphere Surface Temperature Reconstructions: Sensitivity to Methodology,
Predictor network, Journal of Climate, 18, 2308-2329, 2005.
Geophysical Research Letters, 29 (10),
1501, doi: 10.1029/2001GL014554, 2002.
Geophysical Research Letters, 29 (10),
1501, doi: 10.1029/2001GL014554, 2002.
1877
Geophysical Research Letters, 29 (10),
1501, doi: 10.1029/2001GL014554, 2002.
Journal of Climate, 16, 462-479, 2003
85% missing
95% missing
Journal of Climate, 16, 462-479, 2003
85% missing
95% missing
Pseudo-Proxy Model Reconstruction
poor
calibration
and verification
MBH98 and other
CFR Methods
guards against
this!
von Storch et al. 2004
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
“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.
Influence of Natural Radiative Forcing
Crowley, T.J., Causes of Climate Change Over the Past 1000
Years, Science, 289 270-277, 2000.
Volcanism
1000
1200
1400
1600
Solar
“Maunder
Minimum”
1800
2000
European Winter Cooling During the Little Ice Age
Empirical
LIA winter cooling in
Europe associated with
an NAO trend due to solar
irradiance changes,
interacting w/
stratospheric
atmospheric dynamics
and chemistry
NASA/GISS Model
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, 21492152, 2001.
Volcanic Radiative Summer Cooling
Ensemble average summer (Jun-Aug) surface temperature
response following eruption of Pinatubo.
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 Winter Dynamical Warming
Ensemble average winter (Dec-Feb) surface temperature
response following eruption of Pinatubo.
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.
Mid-Latitude Summers
Greater variability?
Esper, J., Cook, E.R.,
Schweingruber, F.H., LowFrequency Signals in Long
Tree-Ring Chronologies for
Reconstructing Past
Temperature Variability,
Science, 295, 2250-2253,
2002.
Mid-Latitude Summers
Greater variability?
1000
1200
1400
1600
1800
2000
Annual average
late 17th vs late
18th Century
Temperature change
Proxy based
reconstruction
GCM Solar +
Volcanic patterns
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, 40944107, 2003.
1998 Global Temperature Pattern
Theoretical mechanism for natural
radiative forcing of El Nino
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)
Theoretical mechanism for natural
radiative forcing of El Nino
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.
Response to Volcanic Forcing
Composite Nino3 (100 realizations of CZ model)
Tropical Volcanic radiative forcing (0.1 x W/m2)
Theoretical mechanism for natural
radiative forcing of El Nino
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.
Superposed Epoch
Analysis AD 1649-1868
Superposed Epoch
Analysis AD 1000-1999
all (7) tropical events
exceeding -2 W/m2
All (7) tropical events
exceeding -4 W/m2
Tropical volcanic radiative forcing (0.1 x W/m2)
Theoretical mechanism for natural
radiative forcing of El Nino
Composite Nino3 (100 realizations of CZ model)
Tropical Solar radiative forcing (W/m2)
Tropical volcanic radiative forcing (0.1 x W/m2) 40 year smooth
Theoretical mechanism for natural
radiative forcing of El Nino
Response to Solar Forcing
Composite Nino3 (100 realizations of CZ model)
40 year smooth
Tropical Solar radiative forcing
(W/m2) (40 year smooth)
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.
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 the Tropical Pacific Over the Past 1000 Years, Journal of
Climate, 18, 447-456, 2005.
El Nino and North American
Drought
El Nino vs. North American Drought
over the Past Century
Increased Drought
Less Drought
La Nina
El Nino
Courtesy of
E.Cook
Linear
correlation
coefficient (r)
is not a viable
measure of
statistical
reconstructio
n skill