What role can climate models play in
understanding the Pacific climate history?
Caspar Ammann
NCAR
What role can climate models play in understanding the Pacific
climate history?
Testing and understanding external
forcings and their impacts
Caspar Ammann
NCAR
Simulations of the 20th century
All forcings
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Natural only
Meehl et al. 2004
Overview Forcings
• Global mean: changes in
radiative balance
– Timing
– Consistency of signal over
time
– Consistency over different
time scales?
• Regional climates:
combination of direct
radiative forcing and
dynamics
– Connection to internal
modes of variability
– Modulation of modes by
radiative forcing?
Natural External Forcings
Internal variability
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Paleo Data:
11-Year
Background trend or not?
Solar Magnetic Models: Wang/Lean, 2005
Century-scale
14-C/10-Be Muscheler et al., 2006
Wavelength-Dependent Changes
Solar Maximum and Minimum
100 %
10 %
1%
0.1 %
Marsh et al. (2007)
Data from Woods et al. (2002)
OzoneTemperature
Concentration
Changes
Calculated
Trends,
1950-2003
and Spectrally-Dependent
Heating
Global-means, deseasonalized
4K
100 km
-2 K
3K
80 km
-2 K
3K
50 km
-3 K
0.8 K
Rolando Garcia
-0.8 K
25 km
Volcanic Sulfur : Polar Ice Core Record
Tambora Sulfate Flux
19 cores Antarctica
23 cores Greenland/Arctic
Kuwae Signal ~1453 AD in Polar Ice
S-Hemisphere Cores
N-Hemisphere Cores
Gao-Robock-Ammann 2006; in review
Two Long Volcanic Forcing Reconstruction
(New one submitted: Gao-Robock-Ammann)
Crowley 2000; Ammann et al. 2007
Tambora Forcing
using Idealized Transport Assumptions
Horizontal column opt. depth
Vertical Mass Distribution
Limulations Last Millennium
Volcanoes
Sun
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Greenhouse Gas
IPCC 2007
Ammann et al., 2007
Solar Forcing in CSM 1.4 “Millennium Runs”
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Ammann et al., 2007
The ~200-Year Solar ‘Fingerprint’
“Window of Opportunity”
Ammann & Joos
A.D. 700
800
900
1000
1100 1200 1300
1400
“Solar forcing”
NH mean
NH Extra-tropics
(NW. Europe -NW. Siberia)
Mongolia
De Bilt Holland-Wi
-Su
Greenland: isotopes
E.China
Tibetan ice
S.African: speleothem
New Zealand trees
Tasmanian trees
E. Antarctic isotopes
Dronning Maud ice
Argentina trees
Andean ice
Bradley et al., 2003
Radiative Cooling Episodes: Medieval to Present
Cool Episodes
Warm
920-
125014251080- / 1200- 1350-
1580 / 1640- 180817301920-
Reconstructions of Large Scale Climate
Interrupted / Intermittent
Medieval Anomaly
~850-1250
Modern Transition
Natural to Anthrop.
~1920-…
Interrupted / Intermittent
Little Ice Age Episodes
~1260-1850
Systematic Pacific Response?
Annual Time Scale:
Volcanic
Adams et al. 2003
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Van Loon et al. 2007
Century Scale:
Solar?
Cook et al., 2004
Decadal Time Scale:
Solar / Volcanic?
Dynamical Response:
How much doe we understand?
Old Millennium Simulation
CSM - Longterm
CCSM 3.5 with improved ENSO
but no spectral resolution of the cycle
Increased Solar:
Cooling in E-Pacific
Increased Volcanism:
Warming in E-Pacific
Summary
• Forcing Statistics quite well established
• Forcing magnitudes uncertain but can be constrained
• If climatic changes were driven by external forcing,
timing and systematic response are important indicators
• Combination of externally driven (nudged probabilities?)
and internal variations probably most likely: expect
general agreement, but not exclusive
• Ongoing effort at NCAR: Run Process studies with
WACCM and Millennial Simulations with new volcanic
and solar implementations in CCSM
• New Models help to study processes, but Proxy Record
provides the benchmarks.
•
Can we define the key benchmarks for the understanding of past 1500
years? (e.g. key transition periods, retention of mean after change, crosstime scale agreement of signals…)
Simulation of Trends with Models
Models reasonably reproduce
changes in:
• Global and continental scale
evolution of temperature
• Vertical temperature profile
• Atmospheric moisture
• Heat content of oceans
• sea ice retreat in all seasons
•…
Surface Temperatures : Past - Present - Future
Ammann et al., 2007
Tropical Pacific Marine Proxy Network
Palmyra vs Tree-Ring
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Cool, La Nina-like Medieval?
C-Z Model with full solar and volcanic forcing
Combined response to Solar
+Volcanic Forcing
Ensemble mean
Nino3 (100
realizations of CZ
model)
Palymra coral
isotopes (standardized
to have same mean and
standard deviation as
Nino3 composite series)
40 year
smooth
Mann et al., 2003
Precipitation : Regional Changes
Is the current drought just the beginning?
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IPCC Distribution Multi-Model Outlook:
20th century
21st century
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Seager et al. 2007
Projected Patterns of Precipitation Change
Model Simulations
IPCC
Precipitation increases very likely in high latitudes
Decreases likely in most subtropical land regions
This continues the observed patterns in recent trends
Dai & Trenberth 2006
Observed Trends
Paleoclimate Data : Millennial
Ice Rafted Debris in the North Atlantic (Beer/Bond, 2005)
Wood / Peat in Mid-Latitude Mountains (Schluechter, 05)
Paleoclimate Data : Centennial
Dust Records in mid- and high-latitudes
E-China Sea, Xiao et al., 2006
Dome C & Vostok, Antarctica
Delmonte et al., 2005
Paleoclimate Data : Multi-Decadal
Neff et al., 2001
Black et al., 2004
The ~200-Year Solar ‘Fingerprint’
“Window of Opportunity”
CSM simulated Relationship
Response
Expected Relationship
Forcing
Forcing
Ammann & Joos
PR Challenge I
Sun-Climate-Link
• Global/Hemisphere: direct influence of TSI
• Regional: Atmospheric circulation and coupled
Ocean-Atmosphere response
• Big unknowns, targets for collaboration:
– Solar effects on tropical circulation
– Potentially large impact on regional atm. circulation, far field
– Long-term solar variability on centennial-millennial time scale
• Goal: Improve regional climate prediction; but
how to do with the current “Climate Change”
Models (no significant change in sight)?
PR Challenge II
“Paleoclimate Reconstruction” Challenge”
1.
Use state-of-the-art coupled GCM runs
–
–
2.
3.
Existing
Blind-test
Simulate Climate Proxies from model data
Challenge reconstruction community to estimate what “true”
climate looks like
–
–
–
Hemispheric temperature, precip/drought-wetness
Forced vs internal variability signal
Regional variability
Goal: demonstrate what can be geophysically explained; identify where
proxy record and/or reconstruction techniques miss important
signals (requires a realistic idea of regional circulation/climate
response to forcing)
Solar effects in the Pacific : 11-year Cycle
Observations
SST anomalies
during peak years
of the solar cycle
(1856-2004)
Van Loon & Meehl
NCAR PCM(all forcing) - CCSM 3.0
Temperature and Precipitation
IPCC AR4 Models: Surface Temperatures
Solar 11-year Max - Climatology
NCAR CCSM 3.0
GISS e_h
GFDL 2.1
MICRO med-res
ENSO - the largest mode of variability:
The Holy Grail of regional prediction?
Short Time scales: Volcanic eruptions?
Longer time scales: Solar forcing?
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Drought Record
from Tree-Ring Data
Solar Forcing could be the “Rosetta
Stone” to regional dynamics
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• Short observations and
models: Greek
• Solar forcing and its impact
in paleorecords: Demotic
Text
• Geophysical Process:
Hieroglyphs
Simulation of Seasonal Volcanic
Effect on Europe