IPCC Report Relies on RCP 8.5 Despite Determining It a Low Likelihood Scenario

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The United Nations released a new report by the Intergovernmental Panel on Climate Change (IPCC) on the current state of climate change. Today’s report is the sixth assessment of climate science since the IPCC was created in 1988.

CEI Senior Fellow Marlo Lewis said:

“Like previous IPCC reports, AR6 relies on inflated emission baseline scenarios and overheated climate models.

“The IPCC concedes what many have contended all along by admitting ‘the likelihood of high emissions scenarios such as RCP8.5 . . . is considered low.’ Indeed, emissions in 2050 in the International Energy Agency’s current and stated policies scenarios are less than half the quantities projected by RCP8.5. The IPCC also tacitly acknowledges RCP8.5 no longer qualifies as a ‘no policy’ scenario since the vast majority of countries have climate policies.

“And yet, IPCC references RCP8.5 (and an equivalent emission scenario called SSP5-8.5) 1,359 times–more often than any other scenario. Maybe that’s why the IPCC declines to assess the ‘feasibility or likelihood’ of ‘individual scenarios’—otherwise RCP8.5 would be banished from the report!

“The other main problem is the IPCC’s reliance on CMIP6—a group of models that ‘show a higher average climate sensitivity than CMIP5 and the AR6 assessed best estimate.’ CMIP5 was already inaccurate, projecting nearly three times as much warming than observed in the bulk tropical atmosphere. Why rely on models that are hotter still and more sensitive than the IPCC’s ‘best estimate?’”

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