In a weekend filled with social media activity, former US President Donald Trump took to his platform to express his disdain for a specific emissions scenario known as “RCP8.5,” often utilized in global climate change projections. Trump’s post, which quickly gained traction among conservative media outlets, misrepresented the scenario’s role and the Intergovernmental Panel on Climate Change (IPCC)’s involvement.
RCP8.5, a scenario depicting extremely high carbon emissions and extensive global warming, was labeled by Trump as “wrong, wrong, wrong,” asserting that the UN climate committee had admitted its inaccuracy. This claim is unfounded, as the IPCC has not labeled any emissions scenario as incorrect. Trump’s remarks coincided with the unveiling of new emissions scenarios that exclude RCP8.5’s extreme assumptions but still suggest significant challenges in keeping global temperatures from rising more than 1.5C.
Trump’s Statements on RCP8.5
On the evening of May 16, Trump posted a provocative message on Truth Social, criticizing “Dumocrats” and alleging that the UN’s “top climate committee” had acknowledged the errors in RCP8.5. This statement was quickly echoed by conservative media, including the New York Post and the Daily Caller, both of which inaccurately represented the IPCC’s role in developing the scenario.
Despite the claims, the IPCC does not generate climate scenarios itself. Instead, scenarios are created by research groups for use by climate scientists around the world. This misunderstanding was further propagated by media outlets like Fox News and The Australian.
Understanding RCP8.5
Developed in the early 2010s, RCP8.5 was one of four Representative Concentration Pathways (RCPs) designed to represent a spectrum of potential future emissions. It was not intended as a prediction but as a hypothetical scenario to explore the high-risk consequences of unchecked emissions.
The scenario assumes no climate policy interventions and projects significant warming, with the IPCC’s fifth assessment report estimating a temperature increase of 4.3C by the century’s end. Today, the scientific community largely views RCP8.5 as a low-probability scenario, though it remains a useful tool for illustrating extreme outcomes.
The Shift Away from RCP8.5
As part of the IPCC’s ongoing seventh assessment cycle, new scenarios have been developed to replace the RCPs, reflecting advancements in climate science and policy. These new scenarios, outlined in a recent study, present a narrower range of future emissions, acknowledging that both extremely high and low emissions pathways are now less plausible given current trends.
The new high-emissions scenario forecasts a warming of about 3.2C by 2100, a significant reduction from RCP8.5’s projections. This adjustment indicates progress in climate action but also underscores the challenges that remain.
The Role of the IPCC in Scenario Development
Contrary to some public perceptions, the IPCC does not create emissions scenarios. Instead, this task falls to the Coupled Model Intercomparison Project (CMIP), which coordinates climate modeling efforts globally. The IPCC evaluates these scenarios within its assessments but does not dictate their development or retirement.
The ongoing CMIP7 phase will provide the models for the IPCC’s next major reports, incorporating these new scenarios to offer a comprehensive view of potential climate futures. As such, the IPCC continues to play a crucial role in synthesizing and interpreting climate science for policymakers worldwide.
Original Story at www.carbonbrief.org