Investments and Macroeconomic Costs in Climate Mitigation in the Working Group III Contribution to the Fifth Assessment Report of the IPCC

Trainer (2017) criticizes cost estimates of climate change mitigation presented in the Working Group III Report to the IPCC and is concerned by lack of transparency and dubious practices in summarizing the literature. This commentary shows that this critique is based on several mistakes. Trainer (2017) mixes evidence on investment changes and evidence on macroeconomic costs, which are discussed in two different parts of the report because they are different indicators of the economic impact of climate mitigation policy. This commentary also argues that when the report was prepared evidence on investments in mitigation technologies was limited but methodologically sound and transparently reported, contrary to what suggested by Trainer (2017).