the polar amplification of global warming in the absence of the ice albedo feedback
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The Polar Amplification of Global Warming in the Absence of the Ice Albedo Feedback. Aaron Donohoe and David Battisti University of Washington. - PowerPoint PPT PresentationTRANSCRIPT
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The Polar Amplification of Global Warming in the Absence of the Ice
Albedo Feedback
Aaron Donohoe and David Battisti University of Washington
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Annual Mean Temperature change in AGCM (CAM4)simulation of Last Glacial Maximum (LGM) and four
times CO2 (Quad) as compared to pre-industrial (PI)
Latitude
Delta Temperature (K)
Delta Temperature (K)
(Data : Camille Li)
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Meridional anomaly of annual mean temperature change
Latitude
•Surface Polar Amplification
•Indication of the Opposite Aloft
-4
0
42
-2K
5
0 K
-5
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Seasonal Cycle of Temperature
•Smaller amplitude surface seasonal cycle in warmer climate •Opposite true aloft
Latitude
K
K
Seasonal Amplitude of Temperature – PI run
Change in Seasonal Amplitude of Temp.
K
5
0
-5
0
2
-2
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How does the system respond to CO2
only?
• GFDL 2.1 AGCM coupled to a 50 meter slab ocean
• NO LAND - aquaplanet
• NO ICE
• Ensemble of runs with 180 ppm (LGM),
350 ppm (P ), and 1300 ppm (QUAD) CO2
(Thanks to Dargan Frierson)
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Aquaplanet Temperature Changes
Annual Mean
Annual Mean, Meridional AnomalyQUAD - LGM
K
K
K
K
QUAD - LGMSeasonal Amplitude
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QUAD – LGM Change in global annual mean energy budget
SURFACE
ATMOSPHERE
LWA↓
-48.5
+48.5
LWS↑
+34.9
-34.9
LWA↑
-0.2
SWABS
+8.2
-8.2
LH
-9.5
+9.5
SENS
+3.9
-3.9
ALL TERMS ARE IN W/m2
SWREF
+0.2
SWTRANS
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Water Vapor as a SW Absorber
SW Heating by Water Vapor
(Chou and Lee 1996)(Figure: Robert RhodeGlobal Warming Art Project)
QUAD – LGMSW heating
0 50 100 150 200 250
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SW absorption and the equator to pole gradient
[S](1-α)
β = +3.5%Absorption
+β[S](1-α)
-β[S](1-α)
+8 W/m2
-8 W/m2
Global Annual Mean Meridional Anomaly of Annual Mean
Tropics Extratropics
-ΔS(1-α)
+βΔS(1-α)
-βΔS(1-α)
+ΔS(1-α)
+βΔS(1-α)
-βΔS(1-α)
+2.5 W/m2
-2.5 W/m2
-2.5 W/m2
+2.5 W/m2
ΔS = Meridional Anomaly of Solar Insolation
+70 W/m2 -70 W/m2
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SW Absorption and the Seasonal Cycle SUMMER SE’ = Seasonal Extratropical Insolation Anomaly
Extratropics Extratropics
+ SE’(1-α) - SE’(1-α)
+ βSE’(1-α)
- βSE’(1-α)+ βSE’(1-α)
- βSE’(1-α)
+140 W/m2
+5.5 W/m2
-5.5 W/m2
-140 W/m2
-5.5W/m2
+5.5 W/m2
Enhanced Seasonal Cycle
Reduced Seasonal Cycle
WINTER
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QUAD – LGM change in meridional anomaly of SW clearsky heating
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(Quad – LGM) Change in seasonal amplitude of clearsky SW heating
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Conclusions•
Warmer planets exhibit SURFACE polar amplification of temperature change and a reduction of the seasonal cycle independent of an ice albdeo feedback
• Enhanced SW absorption by water vapor in a warmer world explains both the polar amplification and the reduction of the seasonal cycle of temperature
• How much might this mechanism contribute to the real world?
Percent Change in Seasonal Cycle – Aquaplanet Simulations
%
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Clearsky SW Heating in Aquaplanet runs
Annual MeanAnnual Mean, Meridional Anomaly
k/day
k/day
k/day
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Water Vapor as a SW Absorber
SW Heating by Water Vapor
(Chou and Lee 1996)(Figure: Robert RhodeGlobal Warming Art Project)
QUAD – LGMSW heating
0 0.5 1.0 1.5 2.0 2.5
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Annual Mean Heat Transport in Aquaplanet Simulations