by R. McKitrick, Oct 14, 2022 in ClimateChangeDispatch
The high and rising costs of climate policy — now including the inability of jurisdictions that bet big on renewables to guarantee enough energy for their citizens to survive the coming winter — don’t just entitle us to question the basis for it: they demand we do so.
Ultimately, the justification for renewables is the view that carbon dioxide emissions have a big effect on the climate that will cause devastating harm at some point in the future. [bold, links added]
Scientists measure the effect using a concept called “Equilibrium Climate Sensitivity” or ECS, which estimates how much long-run average warming will occur as a result of doubling the amount of carbon dioxide in the atmosphere.
Some important new evidence pointing to a low ECS value just emerged in the scientific literature.
ECS has long been uncertain. In 1979 the U.S. National Academy of Sciences estimated it to be between 1.5 and 4.5 degrees Celsius, with a best estimate of 3.0 degrees C.
That range, which runs from “no big deal” to “very bad outcomes,” was accepted by the UN Intergovernmental Panel on Climate Change (IPCC) in its first report in 1990 and thereafter until 2007 when, citing greater warming projections in newer models, it raised the bottom end to 2.0 degrees C.
But over the next few years, literature developed using, not model simulations, but observed warming rates since the late-1800s to estimate ECS.
Its results typically centered around 2.0 C or less. So in 2013, the IPCC reduced the bottom end of the range back to 1.5 C and declined to offer a best estimate. In other words, after three decades climate science hadn’t narrowed the uncertainty at all.
The economic implications of ECS being 2 C rather than 3 C are enormous.