Mitigation scenarios in a world oriented at sustainable development: the role of technology, efficiency and timing

Two different mitigation scenarios for stabilising carbon dioxide concentration at 450 ppmv by 2100 have been developed, based on the recently developed B1 baseline scenario (part of the IPCC Special Report on Emission Scenarios). In both mitigation scenarios, a global uniform carbon tax has been applied as a proxy of pressure on the system to induce a variety of mitigation measures-assuming the presence of some international mechanism for globally cost-efficient implementation of such measures. The two scenarios differ in the timing of mitigation action: early action versus delayed response. Analysis of the scenarios has led to the following findings. First, stabilisation at a carbon dioxide concentration of 450 ppmv from the B1 baseline scenario is technically feasible. In the first quarter/second quarter of this century most of the reduction will come from energy-efficiency and fuel switching options; later on the introduction of carbon-free supply options will account for the bulk of the required reductions. Second, postponing measures foregoes the benefits of learning-by-doing, and, as a result, an early action strategy will at low discount rates lead to reduced mitigation costs compared to delayed response. The most difficult period for the mitigation scenarios is the 2010-2040 period (exact timing depends on early action or delayed response), when 'bending the curve' towards a lower carbon emission system will have to be initiated. Finally, while overall costs seems to be limited, there are large differences in costs and benefits for individual regions and sectors for instance in terms of redirection of investments, changing fuel trade patterns and changing energy expenditures.