https://www.sciencedaily.com/releases/2020/08/200804085912.htm

"Not only are the emissions consistent with RCP 8.5 in close agreement with historical total cumulative CO2 emissions (within 1%), but RCP8.5 is also the best match out to mid-century under current and stated policies with still highly plausible levels of CO2 emissions in 2100," the authors wrote. ." ..Not using RCP8.5 to describe the previous 15 years assumes a level of mitigation that did not occur, thereby skewing subsequent assessments by lessening the severity of warming and associated physical climate risk."

Four scenarios known as Representative Concentration Pathways (RCPs) were developed in 2005 for the most recent Intergovernmental Panel on Climate Change Assessment Report (AR5). The RCP scenarios are used in global climate models, and include historical greenhouse gas emissions until 2005, and projected emissions subsequently. RCP 8.5 assumes the greatest fossil fuel use, and a resulting additional 8.5 watts per square meter of radiative forcing by 2100.