RCP8.5 as BAU Study of the Day

For my collection, another misuse of RCPs makes it into scientific literature and then into headlines in major media. More after the jump …

USA Today:  “Bye-bye beaches? Half of the world’s beaches could disappear by 2100 because of severe erosion linked to climate change, a study published Monday suggests… The study’s authors calculate that up to 40% of shoreline retreat could be prevented by reducing the greenhouse gas emissions that are driving climate change…”

Time: “Scientists say that half of the world’s sandy beaches could disappear by the end of the century if climate change continues unchecked…“What we find is that by the end of the century around half of the beaches in the world will experience erosion that is more than 100 meters,” said Michalis Vousdoukas. “It’s likely that they will be lost.””

CNN: “The researchers did find that humans have some control over what happens to the world’s beaches. If the world’s governments are able to stick to modest cuts to heat-trapping gas pollution, the researchers found that 17% of projected beach losses by 2050 could be prevented, a number that grows to 40% by 2100 if greenhouse gases are limited. “By trying to accomplish the Paris agreement goals, we can reduce 40% of the impacts that we project in our study,” Vousdoukas said.”

The paper (Vousdoukas et al. 2020) clearly utilizes RCP8.5 as a reference scenario (i.e., effective a BAU scenario) and then compares it to RCP4.5 to estimate benefits of mitigation. Both the use of RCP8.5 as a reference scenario and a comparison with RCP4.5 to estimate benefits of mitigation are methodologically flawed.