Scientists retire RCP8.5 scenario, prompting debate over climate risks

An international team of researchers has revised the standardized emissions scenarios used in climate modeling and abandoned the high-emissions pathway known as RCP8.5, calling it “implausible” given recent energy trends. The move, which affects a scenario cited in thousands of studies, touched off intense debate among scientists and drew public attention, including a response from President Trump who claimed the change showed the projections were wrong.

RCP8.5 was designed as a worst-case exploration, envisioning roughly tripling annual carbon dioxide emissions this century and producing about 4.4 degrees Celsius of warming by 2100. Scientists have used such high-end pathways to test extreme outcomes and probing questions like potential ice-sheet collapse, but many studies and news accounts mistakenly presented RCP8.5 as a business-as-usual forecast.

Critics long argued the scenario relied on an implausible expansion of coal and exaggerated risks. The authors of recent papers and others have pushed for more realistic inputs.

United States

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