Mitigation potentials and costs from sectoral studies
The economic potentials for GHG mitigation at different costs have been reviewed for 2030 on the basis of bottom-up studies. The review confirms the Third Assessment Report (TAR) finding that there are substantial opportunities for mitigation levels of about 6 GtCO2-eq involving net benefits (costs less than 0), with a large share being located in the buildings sector. Additional potentials are 7 GtCO2-eq at a unit cost (carbon price) of less than 20 US$/tCO2-eq, with the total, low-cost, potential being in the range of 9 to 18 GtCO2-eq. The total range is estimated to be 13 to 26 GtCO2-eq, at a cost of less than 50 US$/tCO2-eq and 16 to 31 GtCO2-eq at a cost of less than 100 US$/tCO2-eq (370 US$/tC-eq). As reported in Chapter 3, these ranges are comparable with those suggested by the top-down models for these carbon prices by 2030, although there are differences in sectoral attribution (medium agreement, medium evidence).
No one sector or technology can address the entire mitigation challenge. This suggests that a diversified portfolio is required based on a variety of criteria. All the main sectors contribute to the total. In the lower-cost range, and measured according to end-use attribution, the potentials for electricity savings are largest in buildings and agriculture. When attribution is based on point of emission, energy supply makes the largest contribution (high agreement, much evidence).