Assumptions of Spontaneous Decarbonization in the IPCC AR5 Baseline Scenarios

Projections of future climate change depend upon future anthropogenic greenhouse gas emissions. In preparation for its Fifth Assessment Report, the Intergovernmental Panel on Climate Change implemented a new approach to generating emissions scenarios, called ‘Representative Concentration Pathways’ (RCPs), which replace the scenarios in the ‘Special Report on Emissions Scenarios’ (SRES). The RCPs are designed to provide a range of emissions consistent with a particular radiative imbalance, but projected climate policy actions are heavily influenced by the choice of ‘reference’ or baseline scenario, often derived from the SRES. Here we show that ‘built in’ to the RCP reference cases are some of the same implicit and aggressive assumptions regarding rates of the decarbonization of economic activity found in the SRES [1]. Rates of ‘automatic’ reduction in energy and carbon intensities in the RCPs in the absence of policy are broadly inconsistent with observations from 2000-2008. The ‘stabilization’ pathways