Humans have created a worldwide tragedy through free access to the global common atmosphere. The Conference of the Parties (COP) on climate change increased political commitment to reduce emission from deforestation and degradation and to enhance carbon stocks (REDD+). However, government sectors, political actors, business groups, civil societies, tree growers and other interest groups at different levels may support or reject REDD+. The paper used Arena-Actor-Institution concept to understand REDD+and provides agent-based modeling approach to harnessing its processes. The model explores: (a) how providers are likely to decrease or increase carbon stocks on their landscapes under ‘business as usual' institutions; (b) how they are likely to negotiate with potential buyers with regards to the involvement of brokers (governments or nongovernmental organizations); and (c) how altruism and collaboration can affect the affectivity of REDD+. The model was developed as a spatially explicit model to consider the complexity of REDD+target landscapes. The simulation results are examined against the 3E+criteria, i.e. effectiveness in carbon emission reduction, cost efficiency and equity among involved stakeholders and co-benefit of other activities. This study took the Jambi landscape in Indonesia as a case. The results explain how REDD+agreement areas increase with higher carbon prices, e.g. US25 or US35. However, the simulation also shows that even with low carbon prices GHG emissions will decrease if the altruism degree and collective actions of the actors increases. The paper describes institutional arrangements which would help to harness the global commons of climate change.