A Paucity of Evidence, pt. 5 - Perhaps the most pertinent question regarding global warming is whether carbon dioxide, be it man-made or naturally occurring, is the major determinant of global climate to begin with. Although CO2 is the predominant greenhouse gas, water vapor is a more significant driver of the earth’s greenhouse effect, being more abundant in the atmosphere and having up to ten times the warming effect of CO2. Furthermore, in a widely-cited commentary that was published in the May 2001 issue of the now-defunct journal Chemical Innovation, Robert H. Essenhigh postulated that CO2 does not induce global warming.

In his piece, Dr. Essenhigh suggests that rather than increases in atmospheric CO2 driving global warming, it is global warming – induced by the effect of water vapor on the radiative absorbing/emitting properties of the atmosphere – which accounts for increases of atmospheric carbon dioxide. Professor Essenhigh posits that “the dominant source …for CO2 are the oceans, accounting for about two-thirds of the exchange, with vegetation as the major secondary source,” and that the CO2 contribution to earth’s atmosphere from human generated sources “is within the statistical noise of the major sea and vegetation exchanges, so a priori, it cannot be expected to be statistically significant.”

It would be a tragedy if the sturm und drang regarding global warming were simply a classic mismatch of cause and effect. Given the contradictory research regarding the impact of anthropogenic greenhouse gases on global temperatures and the absence of sound predictive models, the threat of man-made global warming seems to represent coincidence masquerading as causation. It still remains unclear whether greenhouse gases are solely responsible for recently observed global climate changes. Scientists who have attempted to look at the earth’s climate over the last millennium have concluded that temperature fluctuations have been a part of the climatological history of the earth, and that significant climate change certainly occurred long before the development of the combustion engine.

The work of many other scientists suggests that our understanding of the water cycle and its impact of water vapor in the atmosphere is incomplete at best; when water vapor and other natural factors (e.g.: the carbon cycle) are included, man’s contribution to the overall greenhouse effect may yet be infinitesimal. At this point, any discussion of global warming beyond the context of the hypothetical is based more on faith in pseudo-scientific canon than in scientific fact.

Moreover, the public’s opinion of the causes and seriousness of global warming are far from unanimous, as verified by a July 2006 Pew Research Center survey entitled “Little Consensus on Global Warming.”

Roughly four-in-ten (41 percent) believe human activity such as burning fossil fuels is causing global warming, but just as many say either that global warming has been caused by natural patterns in the earth’s environment (21 percent), or that there is no solid evidence of global warming (20 percent).

The public also is divided over the gravity of the problem. While 41 percent say global warming is a very serious problem, 33 percent see it as somewhat serious and roughly a quarter (24 percent) think it is either not too serious or not a problem at all. Consequently, the issue ranks as a relatively low priority, well behind education, the economy, and the war in Iraq.