The dire results of anthropogenic global warming have become passé. Treated by the news media and climate alarmists as established scientific fact, the IPCC’s vision of a dystopian future, a world ravaged by global warming, is fed to our children in school, TV shows and Hollywood movies.
What is never mentioned is that even the IPCC’s predictions encompass several ranges of possible outcome, all predicated on a seemingly simple but mysterious factor called climate system sensitivity. A recent study, published in the journal Science, used spatially more complete paleoclimate data for the Last Glacial Maximum (LGM) in an effort to improve previous estimates of climate sensitivity. The new results have not been widely reported in the news media because, according to the researchers, “these results imply a lower probability of imminent extreme climatic change than previously thought.”
According to a team of researchers led by Andreas Schmittner from Oregon State University, “climate sensitivity is the change in global mean near-surface air temperature ΔSAT caused by an arbitrary perturbation ΔF (radiative forcing) of Earth’s radiative balance at the top of the atmosphere with respect to a given reference state.” More simply put, sensitivity to a forcing—carbon dioxide (CO2) for example—is based on measured change from a base equilibrium state to a new equilibrium state. The equilibrium climate sensitivity (ECS) for a doubling of atmospheric CO2 concentrations, denoted ECS2xC, has been estimated at 3 ± 1.5 °K, an estimate that has remained unchanged for the past three decades. Noting that this value suggests “a large uncertainty,” Schmittner et al. set out to improve that estimate. As described in an accompanying perspective article, by Gabriele C. Hegerl and Tom Russon, the study work was described this way: