Regionally Differentiated Scenarios of Future Albedo Forcing from Anthropogenic Land Cover Change

Monday, 15 December 2014
Andrew D Jones1, Katherine V Calvin2, William Collins1 and James Edmonds3, (1)Lawrence Berkeley National Laboratory, Berkeley, CA, United States, (2)Joint Global Change Research Institute, Pacific Northwest National Laboratory, College Park, MD, United States, (3)Pacific Northwest National Laboratory, Richland, WA, United States
Using the Community Earth System Model (CESM), we develop geographically differentiated estimates of radiative forcing from albedo change associated with major land cover transitions across 151 regions globally. The regions are formed through the intersectrion of 18 agro-ecological zones with 15 geo-political units, and correspond to the agricultural and land-use decision regions utilized by the Global Change Assessment Model (GCAM). Incorporating these forcing factors into GCAM allows us to calculate total radiative forcing associated with alternative scenarios of future anthropogenic land cover change. We find that conversion of 1 km2 of woody vegetation (forest and shrublands) to non-woody vegetation (crops and grassland) yields between 0 to ‑0.71 nW/m2 of globally averaged radiative forcing, depending on regional vegetation characteristics, snow dynamics, and atmospheric radiation environments. Across a set of scenarios designed to span a range of potential future anthropogenic landcover change, we find albedo forcing ranging from ‑0.05 to ‑0.25 W/m2 by 2070. The scenarios vary in terms of assumptions regarding future crop yield growth and climate policies, which could favor either afforestation or bioenergy crops. This range of forcing is similar in magnitude to central estimates for present-day forcing from historical land cover change and to several other forcing agents including nitrous oxide.