DYNAMICAL MECHANISMS OF SOLAR
CLIMATE FORCING IN PAST
CENTURIES
Michael E. Mann
Department of Environmental Sciences, University of Virginia,
Charlottesville, VA
Collaborators: B. Adams, C. Ammann, R. Bradley; J. Brigham-Grette; M.
Cane; A. Clement, T. Delworth; M.K. Hughes; T. Osborn; P. Jones, T.
Rittennour, S. Rutherford; G. Schmidt; D. Shindell; S. Zebiak, Z. Zhang
SORCE Meeting on Decadal Variability in the Sun and Climate
Meredith, NH
Oct 28, 2004
DYNAMICAL MECHANISMS OF SOLAR
CLIMATE FORCING IN PAST
CENTURIES
• Evidence for Solar Periodicities
– The Instrumental Record
– Long-term proxy data and proxy-based
reconstructions
• Model/data comparisons
Bidecadal Variability
in North American
Atmospheric
Circulation and
Drought During the
20th century?
20-22 yr
Zhang, Z., Mann, M.E.,
Coupled Patterns of
Spatiotemporal Variability in
Northern Hemisphere Sea
Level Pressure and
Conterminous U.S. Drought,
Journal of Geophysical
Research, in press, 2004
Bidecadal Variability
in North American
Atmospheric
Circulation and
Drought During the
20th century?
Zhang, Z., Mann, M.E.,
Coupled Patterns of
Spatiotemporal Variability in
Northern Hemisphere Sea
Level Pressure and
Conterminous U.S. Drought,
Journal of Geophysical
Research, in press, 2004
Bidecadal Variability
in North American
Atmospheric
Circulation and
Drought Prior to the
20th century?
Bidecadal Variability
in North American
Atmospheric
Circulation and
Drought Prior to the
20th century?
Solar Forcing and the Western US Bi-Decadal Drought Rhythm:
An Analysis Back to AD 800
Author: Edward R. Cook
Affiliation: Lamont-Doherty Earth Observatory (SORCE ’03!)
The existence of a bi-decadal (~20 years) drought rhythm in the western USA has been documented in instrumental
drought records covering the past 100+ years, and its longer-term existence has been demonstrated as well in long treering reconstructions of past drought extending back to AD 1700. This mode of variability is strongly related to forcing by
the 22-yr Hale solar magnetic cycle and the 18.6-yr lunar nodal tidal cycle (Cook et al., 1997), an interaction that modulates
the overall bi-decadal drought rhythm at centennial timescales. A new drought area reconstruction for the western USA
now extends back to AD 800. This development has provided an opportunity for a much longer evaluation of solar and
lunar tidal forcing to be made then was previously possible. In so doing, the results strongly show that solar and lunar
tidal forcing have jointly influenced bi-decadal drought formation in the western USA for the past 1200 years and probably
much farther back in time. In addition, the long tree-ring-based drought area reconstruction provides evidence for multicentennial drought variability that might indicate longer-term solar forcing as well. This new information is described and
compared to indicators of long-term solar variability in 14C and 10Be records. Overall, the results of this study provide
compelling long-term statistical evidence for solar forcing of drought in the western USA. The challenge now is to
understand the physics behind such forcing so that it can be properly modeled.
Bidecadal Variability in North American Prior to 20th century?
New England Glacial Varves
Raw Varve Thickness
Transformed Varve Thickness
Rittenour, T., Brigham-Grette, J., Mann,
M.E., El Niño-like Climate
Teleconnections in North America
During the Late Pleistocene: Insights
From a New England Glacial Varve
Chronology, Science, 288, 1039-1042,
2000.
Processed (filtered and
standardized) Varve Thickness
Bidecadal Variability in North American Prior to 20th century?
New England Glacial Varves
Raw Varve Thickness
Transformed Varve Thickness
Power Spectrum
(multitaper method)
Rittenour, T., Brigham-Grette, J., Mann,
M.E., El Niño-like Climate
Teleconnections in North America
During the Late Pleistocene: Insights
From a New England Glacial Varve
Chronology, Science, 288, 1039-1042,
2000.
Processed (filtered and
standardized) Varve Thickness
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
Jones, P.D., Mann, M.E., Climate
Over Past Millennia, Reviews of
Geophysics, 42, RG2002,
doi:10.1029/2003RG000143, 2004.
Proxy-based Temperature Reconstructions
in Past Centuries
A
Sensitivity in 10-25
year Cband
B
D
E
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.
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.
Solar Forcing of El Nino?
Decadally-smoothed Mann et al NINO3 (x-1)
Jones et al, Science, 2001
Verschuren et al, Nature, 403, 410-414, 2000.
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.
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
Mann, M.E., Cane,
M.A., Zebiak, S.E.,
Clement, A.,
Volcanic and Solar
Forcing of the
Tropical Pacific the
Past 1000 Years,
Journal of Climate,
in press, 2004.
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 the
Past 1000 Years, Journal of Climate,
in press, 2004.
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
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 the Past 1000 Years, Journal of
Climate, in press, 2004.
Theoretical mechanism for natural
radiative forcing of El Nino
Theoretical mechanism for natural
radiative forcing of El Nino
Courtesy of E.Cook
CONCLUSIONS
•Evidence exists for decadal timescale periodicities in
instrumental and proxy climate records that may be related to
solar forcing
•Decadal timescale signals suggest both thermodynamic and
dynamical responses of the climate to solar radiative forcing.
• Proxy-based climate reconstructions suggest persistent
decadal and multidecadal relationships with solar forcing over
centuries and millennia
•Forced changes in large-scale atmospheric circulation such
as the NAO, and internal dynamics related to El Nino, may
play an important role in explaining regional patterns of
response to solar forcing
Proxy-based Temperature Reconstructions
in Past Centuries
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:
RECONSTRUCTIONS ONLY; Boreholes—Rutherford and Mann (2004); Crowley & Lowery (updated)]
Proxy-based Temperature Reconstructions
in Past Centuries
A
0.3
1375
0.2
1374
0.1
MPI
1373
0.0
Temperature (°C)
1371
-0.2
1370
-0.3
-0.4
HS93 irradiance
1369
-0.5
1368
-0.6
1367
1660 1680 1700 1720 1740 1760 1780 1800 1820 1840
B
1371
0.3
0.2
0.1
1370
proxy
1369
0.0
-0.1
1368
-0.2
1367
-0.3
-0.4
-0.5
Irradiance (W/m2)
1372
-0.1
Estimating
Sensitivity from
Model/Data
comparisons
1366
GISS
1365
LBB95 irradiance
-0.6
1364
1650 1675 1700 1725 1750 1775 1800 1825 1850
Year
Waple, A., Mann, M.E.,
Bradley, R.S., Long-term
Patterns of Solar Irradiance
Forcing in Model
Experiments and Proxybased Surface Temperature
Reconstructions, Climate
Dynamics, 18, 563-578, 2002.
A
Proxy-based Temperature Reconstructions
B
in Past Centuries
Sensitivity on
timescales > 40 year
C
D
Waple, A., Mann, M.E.,
Bradley, R.S., Long-term
Patterns of Solar Irradiance
Forcing in Model
Experiments and Proxybased Surface Temperature
Reconstructions, Climate
Dynamics, 18, 563-578, 2002.
Decadal Variability in
the Great Salt Lake
Level During the 20th
Century
Mann, M.E., Lall, U., Saltzman,
B., Decadal-to-century scale
climate variability: Insights
into the Rise and Fall of the
Great Salt Lake, Geophysical
Research Letters, 22, 937-940,
1995
Quasi-Decadal Variability in North
American Atmospheric Circulation
During the 20th Century
Mann, M.E., Lall, U., Saltzman,
B., Decadal-to-century scale
climate variability: Insights
into the Rise and Fall of the
Great Salt Lake, Geophysical
Research Letters, 22, 937-940,
1995
Quasi-Decadal Variability in North
American Atmospheric Circulation
During the 20th Century
Mann, M.E., Lall, U., Saltzman,
B., Decadal-to-century scale
climate variability: Insights
into the Rise and Fall of the
Great Salt Lake, Geophysical
Research Letters, 22, 937-940,
1995
Quasi-Decadal Variability in North
American Atmospheric Circulation
During the 20th Century
Mann, M.E., Lall, U., Saltzman,
B., Decadal-to-century scale
climate variability: Insights
into the Rise and Fall of the
Great Salt Lake, Geophysical
Research Letters, 22, 937-940,
1995
Bidecadal Variability
in North American
Atmospheric
Circulation and
Drought During the
20th century?
Zhang, Z., Mann, M.E.,
Coupled Patterns of
Spatiotemporal Variability in
Northern Hemisphere Sea
Level Pressure and
Conterminous U.S. Drought,
Journal of Geophysical
Research, in press, 2004