ORIGINAL PAPER The biogeophysical effects of extreme afforestation in modeling future climate Ye Wang & Xiaodong Yan & Zhaomin Wang Received: 11 June 2013 /Accepted: 26 December 2013 # Springer-Verlag Wien 2014 Abstract Afforestation has been deployed as a mitigation strategy for global warming due to its substantial carbon sequestration, which is partly counterbalanced with its biogeophysical effects through modifying the fluxes of ener- gy, water, and momentum at the land surface. To assess the potential biophysical effects of afforestation, a set of extreme experiments in an Earth system model of intermediate com- plexity, the McGill Paleoclimate Model-2 (MPM-2), is de- signed. Model results show that latitudinal afforestation not only has a local warming effect but also induces global and remote warming over regions beyond the forcing originating areas. Precipitation increases in the northern hemisphere and decreases in southern hemisphere in response to afforestation. The local surface warming over the forcing originating areas in northern hemisphere is driven by decreases in surface albedo and increases in precipitation. The remote surface warming in southern hemisphere is induced by decreases in surface albedo and precipitation. The results suggest that the potential impact of afforestation on regional and global cli- mate depended critically on the location of the forest expan- sion. That is, afforestation in 0°–15°N leaves a relatively minor impact on global and regional temperature; afforesta- tion in 45°–60°N results in a significant global warming, while afforestation in 30°–45°N results in a prominent region- al warming. In addition, the afforestation leads to a decrease in annual mean meridional oceanic heat transport with a maxi- mum decrease in forest expansion of 30°–45°N. These results can help to compare afforestation effects and find areas where afforestation mitigates climate change most effectively com- bined with its carbon drawdown effects. 1 Introduction Forests provide a wide range of economic and social benefits to humankind. These include contributions to the overall economy mainly through employment, processing, and trade of forest products as well as investments in the forest sector. They also include the hosting and protection of sites and landscapes of high cultural, spiritual, or recreational value. Furthermore, forests and trees are important carbon sinks which absorb about 2.4 billion tons of carbon dioxide each year or approximately 30 % of all CO 2 emissions from fossil fuel burning and deforestation (Nabuurs et al. 2007; Canadell et al. 2007; Canadell and Raupach 2008; Khatiwala et al. 2009; Pan et al. 2011; Bala et al. 2013). Carbon sequestration by forests has attracted much interest as a mitigation approach, as it has been considered a relatively inexpensive means of addressing climate change immediately. In addition, affores- tation influences the climate via multiple biophysical feed- backs, such as by modifying surface albedo, surface rough- ness length, and evapotranspiration (Field et al. 2007; Bonan 2008; Chapin et al. 2008; Anderson et al. 2011). These bio- physical feedbacks may offset the beneficial effects of carbon sequestration (Anderson et al. 2011). Various studies have simulated the biophysical effects of afforestation and discussed their causes, while the sign of Y. Wang (*) College of Civil Aviation, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China e-mail: wytea@126.com Y. Wang : X. Yan Key Laboratory of Regional Climate-Environment for East Asia, Chinese Academy of Sciences, Beijing 10029, China X. Yan State Key Laboratory of Earth Surface Processes and Resource Ecology (ESPRE), College of Global Change and Earth System Science, Beijing Normal University, 19 Xinjiekouwai StreetHaidian District Beijing 100875, China Z. Wang British Antarctic Survey, Cambridge CB3 0ET, UK Theor Appl Climatol DOI 10.1007/s00704-013-1085-8