Editors at National Review Online assess the current state of climate alarmism.
“The science” should not be a thing. Science is not dogma, but a voyage of endless intellectual exploration in which blind alleys are part of the process. Some scientific facts may be “settled,” but that’s a difficult determination when we are discussing projections far into the future.
And so we come to Representative Concentration Pathway (RCP) 8.5. This was the gloomiest of the four main scenarios prepared for the U.N. Intergovernmental Panel on Climate Change (IPCC) in 2014. Each “pathway” described what was thought would happen if greenhouse gases reached a certain concentration in the atmosphere. If RCP8.5 was followed, the “likely” increase in mean global surface temperature by 2100 would have been 2.6-4.8°C, with a mean of 3.7 °C, a large-scale increase.
RCP8.5 — and its roughly analogous but supposedly more sophisticated successor model, known as SSP5-8.5 — was always intended as an extreme scenario, but alarmist advocates and journalists often portrayed it as a baseline. Now, these trajectories have been found to have become “implausible” by the committee responsible for setting out the scenarios for the next IPCC assessment.
President Trump reacted to the news with glee: “GOOD RIDDANCE! After 15 years of Dumocrats promising that ‘Climate Change’ is going to destroy the Planet, the United Nations TOP Climate Committee just admitted that its own projections (RCP8.5) were WRONG! WRONG! WRONG!”
The truth is more complicated. The authors of the paper in which the scenarios were dismissed as “implausible” attributed the downgrade to “trends in the costs of renewables, the emergence of climate policy and recent emission trends,” an explanation that can be seen as a justification of current climate policy rather than a rejection of it.
On the face of it, that’s fair enough. RCP8.5 and SSP5-8.5 have long been described as outliers by more responsible voices in the climate debate, but, wonders AEI’s Roger Pielke, how plausible were they in the first place?
