Representative Concentration Pathway

These pathways (or trajectories) describe future greenhouse gas concentrations (not emissions) and have been formally adopted by the IPCC.

The pathways describe different climate change scenarios, all of which were considered possible depending on the amount of greenhouse gases (GHG) emitted in the years to come.

The lower RCP values, on the other hand, are more desirable for humans but would require more stringent climate change mitigation efforts to achieve them.

[6] A short description of the RCPs is as follows: RCP 1.9 is a pathway that limits global warming to below 1.5 °C, the aspirational goal of the Paris Agreement.

[10]: Figure 2, p. 223 For the extended RCP2.6 scenario, global warming of 0.0 to 1.2 °C is projected for the late 23rd century (2281–2300 average), relative to 1986–2005.

[11] The RCPs are consistent with a wide range of possible changes in future anthropogenic (i.e., human) greenhouse gas emissions, and aim to represent their atmospheric concentrations.

[14] The four RCPs are consistent with certain socio-economic assumptions but are being substituted with the shared socioeconomic pathways which are anticipated to provide flexible descriptions of possible futures within each RCP.

[17][18] According to the IPCC, RCP 4.5 requires that carbon dioxide (CO2) emissions start declining by approximately 2045 to reach roughly half of the levels of 2050 by 2100.

Since the publication of the IPCC Fifth Assessment Report (2014) the likelihood of this RCP has been debated, due to overestimation of projected coal outputs.

[22][23] On the other hand, many uncertainties remain on carbon cycle feedbacks, which could lead to warmer temperatures than projected in representative concentration pathways.

According to a 2021 study in which plausible AR5 and RCP scenarios of CO2 emissions are selected,[27] Across all RCPs, global mean sea level is projected to rise by 0.26 to 0.82 m by the late 21st century.

The extended RCP2.6 pathway assumes sustained net negative anthropogenic GHG emissions after the year 2070.