The Role of Non-CO2 Greenhouse Gases in Climate Change Mitigation: Long-term Scenarios for the 21st Century.

The non-CO₂ greenhouse gases have so far jointly contributed around 40 percent to overall global warming. In this paper we examine the role of non-CO₂ greenhouse gases in meeting long-term climate change targets. For this purpose, we develop climate mitigation scenarios aimed at achieving long-term stabilization of global radiative forcing. We use the MESSAGE model for a thorough bottom-up representation of the six Kyoto greenhouse gases and corresponding mitigation technologies. This approach endogenizes energy feedback effects from mitigation of non-CO₂ gases and takes into account the interplay and side benefits that exist across GHGs. We analyze two mitigation scenarios that stabilize global radiative forcing at 4.5 W/m² as compared to pre-industrial times-one allowing only for CO₂ mitigation and another with multigas mitigation. In addition, we also investigate a lower stabilization level of 3 W/m² and look into the implications this has for abatement strategies. Our approach helps us to identify a portfolio of measures in the energy, industry and agricultural sectors for achieving a proposed climate target. We find that considering the full basket of GHGs improves the effectiveness of the mitigation portfolio resulting in significantly lower costs, especially in the short term. In the long run, the bulk of the emissions reductions are still found to come from CO₂ and this effect becomes more pronounced under the more stringent climate target. This emphasizes the importance of a diverse mitigation portfolio that includes both CO₂ and non-CO₂ related abatement options in meeting long-term climate targets. [ABSTRACT FROM AUTHOR]