Mitigation of short-lived heating components may lead to unwanted long-term consequences

A mitigation strategy for reducing emissions of short-lived heating components such as black carbon (BC) aerosols and ozone precursors to limit global warming has frequently been suggested (Bond, 2007, Grieshop et al., 2009, Hansen et al., 2000, Jacobson, 2002, Molina et al., 2009 and Nature Editorial, 2009). BC emissions influence the radiative balance in several ways through direct and semi-direct aerosol effects, as well as by impacting the surface albedo (Forster et al., 2007), and their net effect is likely a warming that enhances the total man-made warming. However, the role that BC or other short-lived heating components may play in future mitigation strategies must be formulated with caution to avoid unforeseen and unwanted consequences. A near-term mitigation of short-lived heating components could lead to a delayed action on CO2 and other long-lived greenhouse gases and thus an increased long-term warming. A key element is whether policies are designed as a consequence of predicted warming or observed warming. Without a clear strategy, early BC or ozone reductions may even lead to an unexpectedly larger temperature change.