Representative concentration pathways (RCPs) portray possible future greenhouse gas and aerosol concentration scenarios. Scenarios do not substantially differ before mid-century. 

On the Toolkit's location search page, we provide a simple statement about climate change for the county that an individual chooses on the home page. Results come from RCP2-4.5. That pathway is characterized by current trends of social, economic, and technological patterns wherein global and national institutions make slow progress in achieving sustainable development goals. In this scenarios, greenhouse gas concentrations would peak by mid-century.

Because the concentrations of greenhouse 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.