RCP4.5: a pathway for stabilization of radiative forcing by 2100

Abstract

Representative Concentration Pathway (RCP) 4.5 is a scenario that stabilizes radiative forcing at 4.5 W m −2 in the year 2100 without ever exceeding that value. Simulated with the Global Change Assessment Model (GCAM), RCP4.5 includes longterm, global emissions of greenhouse gases, short-lived species, and land-use-land-cover in a global economic framework. RCP4.5 was updated from earlier GCAM scenarios to incorporate historical emissions and land cover information common to the RCP process and follows a cost-minimizing pathway to reach the target radiative forcing. The imperative to limit emissions in order to reach this target drives changes in the energy system, including shifts to electricity, to lower emissions energy technologies and to the deployment of carbon capture and geologic storage technology. In addition, the RCP4.5 emissions price also applies to land use emissions; as a result, forest lands expand from their present day extent. The simulated future emissions and land use were downscaled from the regional simulation to a grid to facilitate transfer to climate models. While there are many alternative pathways to achieve a radiative forcing level of 4.5 W m −2 , the application of the RCP4.5 provides a common platform for climate models to explore the climate system response to stabilizing the anthropogenic components of radiative forcing.

The social cost of atmospheric release

“…I present the valuation of 1 % of current global anthropogenic emissions (2010 values from Thomson et al (2011), including open biomass burning emissions ), a level small enough that it is a marginal change (Fig. 1).…”

RCP 8.5—A scenario of comparatively high greenhouse gas emissions

“…As indicated in the introduction, however, we also use the MESSAGE model for the development of mitigation scenarios that use the RCP8.5 as a baseline. As targets for the mitigation scenarios we adopt forcing levels of 2.6, 4.5 and 6 W/m 2 by the end of the century, which corresponds to the same radiative forcing levels as assumed by the other RCPs in this SI (see van Vuuren et al 2011b;Thomson et al 2011;Masui et al 2011). For each mitigation scenario the MESSAGE optimization model computes least-cost pathways to stay below the specified target.…”

ORACLE 2-D (v2.0): an efficient module to compute the volatility and oxygen content of organic aerosol with a global chemistry–climate model

“…The open biomass burning emissions of organic compounds from savanna and forest fires are based on the Global Fire Emissions Database (GFED version 3.1; van der Werf et al, 2010) and are distributed into LVOCs (20 %), SVOCs (40 %), and IVOCs (40 %) based on the emission factors proposed by May et al (2013). Emissions of anthropogenic LVOCs, SVOCs, IVOCs, and VOCs (i.e., aromatics, alkanes, olefins) from fossil and biofuel combustion are derived from the CMIP5 emission inventory for the RCP4.5 scenario (Thomson et al, 2011). The volatility distribution of anthropogenic emissions to LVOCs (8 %), SVOCs (72 %), and IVOCs (170 %) is based on the findings of Robinson et al (2007) and includes increased factors (the sum of the emission factors is 250 %) to account for missing IVOC emissions from the traditional inventories.…”