This summary for policymakers focuses on climate change mitigation and follows the structure of the Working Group III contribution to the IPCC’s Fifth Assessment Report. This report assessed the literature on the scientific, technological, environmental, economic and social aspects of climate change mitigation. The summary lays out key findings and conclusions, with levels of certainty and error margins determined by the scope, variety, and quality of evidence, and the extent of expert consensus.
The summary begins by discussing the present perception of mitigation, noting that effective mitigation will not be achieved if independent agents continue to advance their own interests. Equity, justice, and fairness all need to be included in the context of mitigation and adaptation, necessitating the inclusion of value judgements and ethical considerations. Furthermore, with so many intersections, uncertainties, and risks, it is important to take account of possible synergies, co-benefits, and maladaptation potential when considering climate policy. The trends within greenhouse gas (GHG) emissions, and their drivers, are then briefly discussed, with a high degree of confidence placed on the continued increase in GHG emissions caused by humans since the 1970’s, during which time an estimated 40 per cent of all emissions since 1750 have been released.
The report outlines mitigation pathways and measures in the context of sustainable development, first in a long-term pathway context, and then broken down by sector. In the long-term, achieving a two degree target will require significant cuts in GHG emissions through large-scale changes in energy and land-use. In worse scenarios, carbon-removal technologies and afforestation will need to be deployed widespread in the second half of the century, while advancing technology makes economic costs difficult to predict. The various sectors analysed include: cross-sectoral pathways and measures; energy supply; energy end-use sectors; agriculture, forestry, and other land-use; and human settlements, infrastructure, and spatial planning. Areas of focus concern efficiency enhancements, behavioural changes, technological change, and economic costs. Robust qualifications to the extensive empirical referencing are featured throughout, before the paper closes with a section on mitigation policies and institutions, split between sectoral and national policies, and international cooperation. Included in this section are warnings that investment patterns will require large changes, and that cap and trade systems have not proven to be constraining on GHG emissions.