The Current Wisdom is a series of monthly articles in which Patrick J. Michaels and Paul C. “Chip” Knappenberger, from Cato’s Center for the Study of Science, review interesting items on global warming in the scientific literature that may not have received the media attention that they deserved, or have been misinterpreted in the popular press.
The biggest criticism to emerge so far regarding the new Fifth Assessment Report from the U.N.’s Intergovernmental Panel on Climate Change (IPCC) is that it generally fails to acknowledge how poorly climate model simulations of the earth’s temperature evolution compare with actual observations. If the models cannot accurately simulate known climate variability and change, using them for policy purposes is a fool’s errand.
There are two lines of evidence that converge to show that the climate models are largely failing to accurately simulate observed climate behavior.
The first is that a collection of about ten research papers (including 16 separate analyses) published in the scientific literature beginning in 2011 that collectively indicate that the earth’s equilibrium climate sensitivity—that is, how much the earth’s average surface temperature rises as a result of a doubling of the atmospheric carbon dioxide concentration—is about 2°C, give or take about 0.5°C (Figure 1). You can find details here.
Figure 1. Climate sensitivity estimates from new research published since 2010 (colored), compared with range of estimates from the climate models incorporated into the IPCC Fifth Assessment Report (AR5; black). The arrows indicate the 5 to 95 percent confidence bounds for each estimate along with the best estimate (median of each probability density function; or the mean of multiple estimates; colored vertical line). Ring et al. (2012) present four estimates of the climate sensitivity and the red box encompasses those estimates. The light grey vertical bar is the mean of the 16 estimates from the new findings. The mean climate sensitivity (3.2°C) of the climate models used in the IPCC AR5 is 60 percent greater than the mean of recent estimates (2.0°C).