Potential for international offsets to provide a net decrease of GHG emissions

At COP 17 in Durban, the Parties called for new market mechanisms, and more broadly, “various approaches, including markets” to “achieve a net decrease and/or avoidance of greenhouse gas emissions”. This paper explores what a net decrease might mean in practice, how it might be achieved, and the potential scale of the net atmospheric benefit that could be attained in 2020. It finds that achieving a net decrease in global GHG emissions hinges on: the ability to generate offset units for which additionality is relatively certain; measures (such as shortened crediting periods or pre-issuance discounts) that lead to more GHG abatement than credited, i.e. surplus reductions; and a means to account for any surplus reduction in a way that it does not simply contribute to meeting an existing GHG reduction pledge. The paper also draws lessons from the Clean Development Mechanism about challenges in attaining a net decrease, and examines the potential for existing CDM project types to produce surplus credits.