Feasible climate targets: The roles of economic growth, coalition development and expectations

The analysis presented here follows the design specified by the Energy Modeling Forum (EMF) Transition Scenarios study on achieving climate stabilization goals with delayed participation by developing countries. We use the MERGE model to evaluate the core EMF scenarios for both the international and the US-specific studies. Our results indicate that a radiative forcing target equivalent to 450 ppmv CO2-e cannot be met even allowing for full participation and overshoot during the entire 21st century. With delayed participation of developing countries, a target of 550 ppmv CO2-e is only attainable with pessimistic assumptions about economic growth, and even then only at very high cost. A target of 650 ppmv CO2-e can be met with delayed participation for a more affordable cost. We highlight sensitivities to the core scenarios in two key dimensions: (i) the effect of the unfolding global financial crisis on the rate of economic growth and (ii) the willingness of initially non-participating countries to agree at the beginning of the next commitment period (i.e. 2012) to join the coalition at a pre-specified date in the future. We find that while the recession does not fundamentally change the crucial role of developing country involvement, advance agreement on their part to future targets could substantially reduce costs for all countries.