What are RCP and SSP scenarios?
In short: Representative Concentration Pathways (RCPs) describe alternative radiative-forcing trajectories used for many CMIP5 projections. Shared Socioeconomic Pathways (SSPs) describe alternative societal development pathways and, in CMIP6 scenario labels, are paired with an approximate forcing level. Both are conditional climate scenarios, not predictions of exactly what society or weather will do.
How to read the labels
An RCP label such as RCP4.5 emphasizes an approximate forcing level by 2100. A CMIP6 label such as SSP2-4.5 combines a socioeconomic pathway number with an approximate 2100 forcing level, so the full label matters.
Using scenarios in impact studies
Researchers normally analyze more than one model and scenario to represent uncertainty. Scenario data should be paired with the corresponding model's historical simulation and processed with consistent variables, units, calendars, and time steps.
Downscale CMIP5 RCP and CMIP6 SSP scenarios to local series with SD-GCM.