View
220
Download
1
Tags:
Embed Size (px)
Citation preview
The Polar Amplification of Global Warming in the Absence of the Ice
Albedo Feedback
Aaron Donohoe and David Battisti University of Washington
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)
Meridional anomaly of annual mean temperature change
Latitude
•Surface Polar Amplification
•Indication of the Opposite Aloft
-4
0
42
-2K
5
0 K
-5
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
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)
Aquaplanet Temperature Changes
Annual Mean
Annual Mean, Meridional AnomalyQUAD - LGM
K
K
K
K
QUAD - LGMSeasonal Amplitude
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
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
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
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
QUAD – LGM change in meridional anomaly of SW clearsky heating
(Quad – LGM) Change in seasonal amplitude of clearsky SW heating
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
%
Clearsky SW Heating in Aquaplanet runs
Annual MeanAnnual Mean, Meridional Anomaly
k/day
k/day
k/day
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
Annual Mean Heat Transport in Aquaplanet Simulations