PNNL

Abstract

We present the greenhouse gas concentrations for the Representative Concentration Pathways (RCPs) and their extensions beyond 2100, the Extended Concentration Pathways (ECPs). These projections include all major anthropogenic greenhouse gases and are a result of a multi-year effort to produce new scenarios for climate change research. We first compiled a suite of observations and emissions estimates for greenhouse gases (GHGs) through the historical period (1750-2005). For the 21st century, we start from emissions projected by four different Integrated Assessment Models for 2005-2100. We harmonize these emissions to allow inter-comparability of scenarios and to achieve a smooth transition from historical data. These harmonized emissions are then used to derive future GHG concentrations. We also present the GHG concentrations for one supplementary extension, which illustrates the emissions implications of attempting to go back to ECP4.5 concentration levels after emissions in the 21st century followed RCP6. Corresponding radiative forcing values are also presented for the RCP and ECPs.