Representative concentration pathways (RCPs) portray possible future greenhouse gas and aerosol concentration scenarios. Scenarios do not substantially differ before mid-century. Because the concentrations of those gases continue to increase at a rapid rate, and because planners want to incorporate a margin of safety in their plans, many professionals use RCP 8.5 for near and long-term projections. For examples of how one state evaluates and uses projections, see Cal-Adapt.