One of the least reliable forms of reasoning is that which goes: we know how much every variable contributes to a particular result except one; therefore, if we account for all of those known variables, whatever remains must be attributable to X. Now, of course, in the realm of mathematics such reasoning is used all the time. Transplanted to other subjects, however, it is generally tendentious.
Years ago, I saw a study that purported to “prove,” scientifically, how much of the disparity in incomes between African-Americans and other Americans was caused by racism. The authors proceeded to identify all relevant differences between African-Americans and others (education, for example) and adjust for those variables. Whatever remained–85 to 90 percent of the total, as I recall–was pronounced to be the effect of racism, without actually identifying or demonstrating any impact of racism whatsoever. In this particular study, some obvious variables–like the effects of culture–were completely absent.
Most laymen do not realize that global warming alarmists do something similar, and equally fallacious. They acknowledge, as they must, that temperatures on earth have fluctuated widely over time as a result of a number of factors–the Sun’s variable energy output, multiple cycles relating to the oceans, and more. The truth is that these factors, and their relationship to the Earth’s climate, are not well understood. But the alarmists simply assume away all difficulties by assigning quantitative assumptions to each of the factors they identify. Whatever is left, they say, must be due to human activity. Ken Haapala, Executive Vice President of the Science and Environmental Policy Project, explains:
Simply put, if one asserts that there are only two possible causes of C, namely A and B; then, if one eliminates A as a possible cause of C, one must conclude B causes C. The fallacy is that one assumes he has complete knowledge of all the possible causes of C.
Such is the case of the [United Nations Intergovernmental Panel on Climate Change] in its 2007 Fourth Assessment Report (AR4). According to the methodology as stated: all the known natural causes “A” of temperature change “C” are calculated, thus all the remaining influences must be human caused, “B.” This methodology assumes all the natural causes of temperature change are known to the IPCC and delineated, which they are not. For example, El Niños are dismissed as being too short in duration to cause temperature trends, but frequency of El Niños may be very important.
At least, authors of the main body of AR4 state that many of the possible natural causes for temperature changes are poorly understood. The authors of the Summary for Policymakers (SPM) included only one possible natural cause – changes in solar irradiance. Thus, the authors of the SPM greatly misled those the SPM was designed to influence, policymakers – and the public.
This is just one of the many ways in which global warming alarmists have systematically tried to mislead the public; which is to say, you and me.