IPCC Fourth Assessment Report: Climate Change 2007
Climate Change 2007: Working Group III: Mitigation of Climate Change Conclusions of bottom-up potential estimates

When comparing the emission reduction potentials as presented in Table 11.4 with the baseline emissions, it can be concluded that the total economic potential at costs below 20 US$/tCO2-eq ranges from 15 to 30% of the total added-up baseline. The economic potential up to 100 US$/tCO2-eq is about 30 to 50% of emissions in 2030. There is medium evidence for these conclusions because, although a significant amount of literature is available, there are gaps and regional biases, and baselines are different. There is also medium agreement on these conclusions because there is literature for each sector with substantial ranges but the ranges may not capture all the uncertainties that exist. Although there are differences in relative mitigation potentials and specific mitigation costs between sectors (e.g. the buildings sector has a large share of low-cost options), it is clear that the total mitigation potential is spread across the various sectors. Substantial emission reductions can only be achieved if most of the sectors contribute to the emission reduction. In addition, there are barriers that need to be overcome if these potentials are to materialize.