1. 1 The Impact of Albedo Change on Carbon Sequestration Strategies Maithilee Kunda Gregg Marland Lorenza Canella Bernhard Schlamadinger Neil Bird

2. 2 What is albedo? albedo = reflected radiation incident radiation albedo = 0.5albedo = 1.0albedo = 0.0

3. 3

4. 4 Land albedo is a function of... Vegetation Snow cover Soil color Elevation and slope Time of day Time of year Latitude... ?

5. 5 Albedos of Different Land Covers

6. 6 Why do we care? land cover change causes albedo change, which effects the surface energy balance in particular, field to forest causes a BIG change, especially in snowy conditions

7. 7 Global effects of albedo change Bonan, Pollard, & Thompson. (1992) “Effects of boreal forest vegetation on global climate.” Nature: 359. – boreal deforestation has a cooling effect – cooling perpetuated by thermal reservoir of oceans and by ice-albedo positive feedback Betts (2000). “Offset of the potential carbon sink from boreal forestation by decreases in surface albedo.” Nature: 408. – albedo warming effect is significant in magnitude compared to cooling effect of carbon sequestration – warming may offset cooling in boreal regions

8. 8 Studying albedo change locally 1 hectare = 10,000 m 2 reforestation of fields – deciduous or coniferous varying latitudes – more snow cover at higher latitudes: more albedo effect – less incoming radiation at higher latitudes: less albedo effect

9. 9 A simple beginning Albedo as a function of – land cover – month – snow cover Simple radiation model using NREL data of average monthly solar insolation – no variable for cloud cover – no hydrologic cycle or latent heat fluxes

10. 10 Example: Caribou, Maine

11. 11 Example: Caribou, Maine

12. 12 The basic logic A change in local carbon stocks Creates a local change in surface albedo Creates a local change in the mean annual radiative flux Causes a global mean annual radiative forcing Which can be equated with a change in atmospheric carbon burden Which we compare to the initial change in local carbon stocks

13. 13 Albedo change to carbon change Mean annual radiative forcing F Atmospheric CO 2 equivalence: F = 5.35 ln (1 +  C / C) Terrestrial carbon equivalence T: T = (Mc / Ma) m  C adapted from Betts, 2000

14. 14 GORCAM

15. 15 The time-scale issue Change in land surface generates a permanent change in surface albedo A pulse of CO 2 to (or from) atmosphere will decay with time as atmosphere equilibrates with the rest of the global carbon cycle Therefore, we treat all flows of carbon as annual pulses and let them decay with time. – CO 2 (t) = CO 2 (initial) {a 0 + ∑a i e -t/zi } for i = 1 to 4; from Maier-Reimer and Hasselman, 1987

16. 16 CO 2 decay function

17. 17 Preliminary results: carbon stock changes - Worcester, MA

18. 18 Preliminary results: carbon stock changes – Caribou, ME

19. 19 Preliminary results: radiative impacts – Worcester, MA 90% Canopy closure

20. 20 Preliminary results: radiative impacts – Caribou, ME 90% Canopy closure

21. 21 Further albedo investigations better albedo representation – vegetation type, growth rates – snow cover, climate-vegetation feedbacks GORCAM model – alternate scenarios involving forest products and bioenergy production ways to think about clouds and latent heat – might temper albedo effect

22. 22 Conclusions Complex system This study only estimates relative magnitudes of albedo effect and sequestration effect, which seem to be comparable Carbon balance is not the whole story Surface energy balances appear to be important and need systematic consideration

23. 23 Acknowledgements DOE Global Change Education Program (GCEP) DOE Office of Science, Biological and Environmental Research (BER)