Good Climate News Isn’t Told: Reporting scientific progress would require admitting uncertainties

By Holman Jenkins.

"So we’ll quote a passage in an exemplary French report that begins, “But uncertainty about how hot things will get also stems from the inability of scientists to nail down a very simple question: By how much will Earth’s average surface temperature go up if the amount of CO2 in the atmosphere is doubled?”

“That ‘known unknown’ is called equilibrium climate sensitivity (ECS), and for the last 25 years the U.N.’s Intergovernmental Panel on Climate Change (IPCC)—the ultimate authority on climate science—has settled on a range of 1.5 C to 4.5 C.”

The French report describes a new study by climate physicists Peter Cox and Mark Williamson of the University of Exeter and Chris Huntingford of the U.K.’s Center for Ecology and Hydrology. Not only does it narrow the range of expected warming to between 2.2 and 3.4 degrees Celsius, but it rules out the possibility of worrying outcomes higher than 4 degrees."

"This question of climate sensitivity goes not just to how much warming we can expect. It goes to the (almost verboten) question of whether the expected warming will be a net plus or net minus for humanity. And whether the benefit of curbing fossil fuels would be worth the cost."

"Leaving climate sensitivity uncertainties out of the narrative certainly distorts the reporting that follows. Take a widely cited IPCC estimate that, “with 95% certainty,” humans are responsible for at least half the warming observed between 1951 and 2010.

This sounds empirical and is reported as such. In fact, such estimates are merely derivative of how much warming should have taken place if the standard climate sensitivity estimate is correct. Imagine predicting an 8 before letting the dice fly, then assuming an 8 must have come up because that’s what your model predicted."

"No better example exists than their gullibility in the face of U.S. government press releases pronouncing the latest year the “warmest on record.” Scroll down and the margin of error cited in the government’s own press release would lead you rightly to suspect that a clear trend is actually hard to find in recent decades despite a prodigious increase in CO2 output.

Well, guess what? Taking account of the actual temperature record and its tiny variations is exactly what the Exeter group and others have been doing in order to make progress on the 40-year problem of climate sensitivity. And they are finding less risk of a catastrophic outcome than previously thought."