1. A Fully Coupled GCM Study of a "Geoengineered World"
D.J. Lunt, A. Ridgwell, P.J. Valdes, A. Seale
Introduction
Experimental Design
Physical Understanding
Impacts
Conclusions + Future Work

2. A Guide to Geoengineering

3. The reality is more complex…..
Annual mean surface temperature change Geoengineered - pre-industrial

4. HadCM3L – fully coupled, full complexity atmosphere + ocean model
no flux correction
3.75o x 2.5o resolution, 19 (20) vertical levels in atmosphere (ocean)
“State of the art”, in particular for >100 year simulations.

5. (1) Pre-industrial (PI) (2) High CO2 (4* PI),
3 simulations:
(1) Pre-industrial (PI)
(2) High CO2 (4* PI),
(3) High CO2 (4* PI), reduced solar constant
4*CO2
4*CO2
Guess 1
17.24oC
12.78oC
12.77oC
Guess 2
Pre-industrial
Guess 3
4.2% = 57 W/m2
Pre-industrial

6. Solar forcing has strong meridional gradient
Solar forcing has strong meridional gradient. CO2 forcing balances in global mean but is more meridionally homogeneous
Solar forcing, TOA
Temperature anomaly, Geo - PreInd

7. Decrease in poleward heat transport, by both atmosphere and ocean.
Atmosphere dominates.
Geo - Preind
Preind

8. Annual mean surface temperature change Geoengineered - pre-industrial

9. Annual mean sea ice change Geoengineered - pre-industrial

10. Ocean circulation Preind meridional Atlantic streamfunction [Sv]
Geo-Preind meridional Atlantic streamfunction [Sv]

11. Precipitation
Soil moisture
Storm tracks (500mbar EKE)

12. Vegetation
Pre-Ind
Geo (climate only)
Geo (climate + CO2)

13. ENSO
Control
Geoengineered

14. Conclusions and Future Work
‘Sunshade’ geoengineering will lead to warmer poles, cooler tropics. Effects amplified by snow and seaice albedo feedbacks.
Decreased intensity of the hydrological cycle.
Decreased Pacific storm tracks
Significant vegetation changes due to high CO2
Reduced ENSO variability
Ocean acifidification?
More realistic time-varying CO2 scenarios, and more realistic sunshade geometry.

15. A new journal for model descriptions… Geoscientific Model Development
Accepting contributions via the webpage NOW!)
First GMD Discussions paper published online 1st January 2008
“Official Launch” at EGU, Vienna 2008
Any questions, contact the Executive Editors: