Representative Concentration Pathways
The Coupled Model Intercomparison Project Phase 5 (CMIP5) projections make use of Representative Concentration Pathways (RCPs), which are designed to provide plausible future scenarios of anthropogenic forcing spanning a range from a low emission scenario characterized by active mitigation (RCP 2.6), through two intermediate scenarios (RCP 4.5 and RCP6.0), to a high emission scenario (RCP 8.5).
Each RCP is associated with plausible combinations of projected population growth, economic activity, energy intensity, and socio-economic development. The RCP scenarios were named based on their total radiative forcing by (or post) 2100.
Summary:
RCP2.6 represents a peak in radiative forcing at approximately 3 W/m2 mid-century before declining to 2.6 W/m2 by 2100.
RCP4.5 represents a stabilization (without overshoot) in radiative forcing at 4.5 W/m2 post 2100.
RCP6.0 represents a stabilization (without overshoot) in radiative forcing at 6 W/m2 post 2100.
RCP8.5 represents a rise in radiative forcing to 8.5 W/m2 in 2100.
These RCP scenarios serve as input to the Earth System Models, which simulate the climate system response and resulting climate conditions.
Figure 1 illustrates the progression of information used to develop these scenarios.
Figure 1
Socioeconomic (top row), energy intensity (second row), greenhouse gas emission (third row), and greenhouse gas concentration (fourth/bottom row) assumptions underlying the representative concentration pathways (RCPs) used to drive future climate projections. From van Vuuren, et al., 2011, reproduced with permission.