The anthropogenic global warming debate experienced a reawakening last month, following the U.S. Environmental Protection Agency’s proposed finding that greenhouse gases contribute to air pollution that may endanger public health or welfare. In an effort to keep the debate from heading far off course, I must comment on one particular argument that is, in my view, nonsensical and ultimately distracts attention away from the interests of the chemical process industries (CPI).
The argument is that carbon dioxide is somehow exempt from being considered a pollutant simply because it is a naturally occurring substance that is essential for plant life — and, therefore, human life. In addition to letters and emails, I’ve seen this argument everywhere from small-town newspapers to well-known trade and consumer publications — and, of course, on their blogs. Each time, numerous contradictions come to mind.
Carbon dioxide is not the first substance with positive use to be classified as a pollutant. Many well-established precedents already exist throughout the CPI. At certain concentrations these substances are indeed valuable — if not essential — to human life. Like the current proposals for regulating carbon dioxide and other greenhouse gases (GHGs), the natural existence of these substances is not controlled. And in many cases, the industrial emission of these substances into the air, water or ground is all but ignored up to a certain point (which is usually defined on the basis of concentration or mass). A simple, yet important fact that is seemingly ignored in the argument "CO2 is automatically exempt from pollutant status" is that the distinction of pollutant applies exclusively to human activities that exceed certain emission thresholds.
Perhaps the simplest of these examples is warm water, which arguably is essential to the developed world but is also classified by the U.S. EPA and others as "thermal pollution" when released into a nearby stream, river, lake or ocean. Indeed, in the design of industrial cooling water systems, warm water discharge is a key consideration (for more see p. 45).
Ozone (O3) is classified as a pollutant even though it naturally sustains life on earth (in the stratospheric ozone layer) and has beneficial commercial applications (such as water treatment). Meanwhile, hydrochloric acid is considered a hazardous air pollutant in the U.S. and elsewhere, yet it is produced naturally by the human body for digesting food.
The point is that once again a group of scientists has developed a hypothesis about the potentially harmful effects of human activities and has presented enough supporting evidence to raise concern in substantial numbers of the scientific community and the public alike. Regulation is now unavoidable. Flawed arguments don’t do anything to change that and actually hurt the interests of CPI by distracting everyone from the important decisions that are already taking place — how those regulations should be defined and carried out.
True industry advocates should instead focus on helping shape greenhouse gas policies that are both effective and realistic in terms of their immediate and longterm impacts on global economics (see a recent Letter to the Editor for more). In this effort, I agree with the premise that more education on greenhouse gases and their effects is needed. But, instead of diverting to carbon dioxide’s life-giving characteristics, which are part of most elementary-school science classes anyhow, I suggest, for one, raising awareness of other, lesser-known greenhouse gases with higher estimated global warming potential. For instance, hydrofluorocarbons, perfluorocarbons, sulfur hexafluoride and N2O global warming impacts are estimated to be 298 – 22,800 times that of CO2 (per unit mass) over a 100 year period.