Comments from S. Fred Singer Submitted to EPA Regarding the Advanced Notice of Proposed Rulemaking for Greenhouse Gases Under the Clean Air Act

The crucial question is: Is warming (predominantly) due to natural or human causes? How can one tell? The issue is of obvious importance since natural causes cannot be influenced in any way by policies that limit greenhouse (GH) gas emissions, such as CO2. Resolving the question is a difficult scientific task. Natural causes are plausible; the climate has been warming and cooling for billions of years on many different time scales [See, e.g., Singer and Avery 2007]. On the other hand, GH warming is also plausible, since the concentration of GH gases has been increasing due to human activities.

Since the major (anthropogenic) greenhouse gas, carbon dioxide, is globally distributed, we need to determine whether the observed rise in CO2 (mainly due to burning of fossil fuels to generate energy) can produce the kind of warming trends calculated by greenhouse models. The key parameter is the so called “climate sensitivity (CS),” usually defined as the increase of global mean surface temperature (GMST) produced by a doubling of global CO2 concentration. The NIPCC and other independent scientists suggest values of about 0.5 C or even lower, far below those of the IPCC.

Published IPCC models give differing values of CS, usually ranging between 1.5 and 4.5 degC. It has become evident that these differences result from different ways in which computer models are parameterized. Depending on assumed parameter values, the climate sensitivity can even be lower than 1.5 and can range up to 11.5 C. These models are the basis of the “evidence” that EPA relies on in the Endangerment Technical Support Document.