The nature and quantity of mitigation options, as well as data availability and quality of the available data, vary significantly across sectors. Even for largely similar mitigation options, a large variety of context-specific metrics is used to express their cost and potentials that involve conversions of input data into particular output formats.For the purpose of the Working Group III (WGIII) contribution to theIntergovernmental Panel on Climate Change (IPCC) Fifth AssessmentReport (AR5), a limited but still diverse set of sector-specific metrics is used to strike a balance between harmonization of approaches across sectors and adequate consideration of the complexities involved.

Mitigation potentials are approached via product-specific or service specific emission intensities, i.e., emissions per unit of useful outputs, which are as diverse as electricity, steel, and cattle meat. Mitigation potentials on a product/service level can be understood as the potential reduction in specific emissions that can result from actions such as switching to production processes that cause lower emissions for otherwise comparable products1 and reducing production/consumption of emission-intensive products.