WHAT IS TO BE DONE?
14.7. WHAT IS TO BE DONE?
Of all environmental hazards, there is little doubt that major disruptions in the atmosphere and climate have the greatest potential for catastrophic and irreversible environmental damage. If levels of greenhouse gases and reactive trace gases continue to increase at present rates, major environmental effects are virtually certain. On a hopeful note, the bulk of these emissions arise from industrialized nations which, in principle, can apply the resources needed to reduce them substantially. The best example to date has been the 1987 “Montreal Protocol on Substances that Deplete the Ozone Layer,” an international treaty through which a large number of nations agreed to cut chlorofluorocarbon emissions by 50% by the year 2000. This agreement and subsequent ones, particularly the Copenhagen Amendment of 1992, may pave the way for more encompassing agreements covering carbon dioxide and other trace gases.
More ominous, however, is the combination of population pressure and desire for better living standards on a global basis. Consider, for example, the demand that these two factors place on energy resources, and the environmental disruption that may result. In many highly populated developing nations, high-sulfur coal is the most readily available, cheapest source of energy. It is understandably difficult to persuade populations faced with real hunger to forego short-term economic gain for the sake of long-term environmental quality. Destruction of rain forests by “slash- and-burn” agricultural methods does seem to make economic sense to those engaged in subsistence farming to obtain badly needed hard currency, which can be earned by converting forest to pasture land and exporting fast-food-hamburger beef to wealth- ier nations.
What is to be done? First of all, it is important to keep in mind that the atmosphere has a strong ability to cleanse itself of pollutant species. Water-soluble gases, including greenhouse-gas CO 2 , acid-gas SO 2 , and fine particulate matter are removed with precipitation. For most gaseous contaminants, oxidation precedes or accompanies removal processes. To a degree, oxidation is carried out by O 3 . To a larger extent, the most active atmospheric oxidant is hydroxyl radical, HO • . As illustrated in Figure 9.10 , this atmospheric scavenger species reacts with all
important trace gas species except for CO 2 and chlorofluorocarbons. It is now generally recognized that HO • is an almost universal atmospheric cleansing agent. Given this crucial role of HO • radical, any pollutants that substantially reduce its concentration in the atmosphere are potentially troublesome. One concern over carbon monoxide emissions to the atmosphere is the reactivity of HO • with CO,
(14.7.1) which could result in removal of HO • from the atmosphere.
CO + HO • → CO 2 + H
Of all the major threats to the global climate, it is virtually certain that humankind will have to try to cope with greenhouse warming and the climatic effects thereof. The measures to be taken in dealing with this problem fall into the three following categories:
• Minimization by reducing emissions of greenhouse gases, switching to
alternate energy sources, increasing energy conservation, and reversing deforestation. It is especially sensible to use measures that have major benefits in addition to reduction of greenhouse warming. Such measures include, as examples, reforestation, restoration of grasslands, increased energy conservation, and a massive shift to solar energy sources.
• Counteracting measures, such as injecting light-reflecting particles into
the upper atmosphere. • Adaptation, particularly through increased efficiency and flexibility of
the distribution and use of water, which might be in very short supply in many parts of the world as a consequence of greenhouse warming. Important examples are implementation of more efficient irrigation practices and changes in agriculture to grow crops that require less irrigation. Emphasis on adaptation is favored by those who contend that not enough is known about the types and severity of global warming to justify massive expenditures on minimization and counteractive measures. In any case, adaptation will certainly have to be employed as a means of coping with global warming.
Potentially, tax strategy can be very effective in reducing use of carbonaceous fuels and greenhouse CO 2 emissions. This is the rationale behind the carbon tax, which is tied with the carbon content of various fuels. Another option is to dispose of carbon dioxide to a sink other than the atmosphere. The most obvious such sink is the ocean; other possibilities are deep subterranean aquifers and exhausted oil and gas wells.
A common measure taken against the effects of another atmospheric hazard, ultraviolet radiation, provides an example of adaptation. This measure is the use of sunscreens placed on the skin as lotions to filter out UV-B radiation. The active ingredient of sunscreen must absorb ultraviolet light effectively, but this is not enough because it is the absorption of ultraviolet light by skin that makes it so dangerous in the first place. Therefore, active compounds in sunscreen formulations
must also dissipate the absorbed energy in a harmless way. 10 The way in which this is done is illustrated below for o-hydroxybenzophenone contained in sunscreens, which reacts as shown by Reaction 14.7.2 at the top of the next page.
The first step in the above reaction sequence can be regarded as intramolecular transfer of energy and internal (spontaneous) isomerization (see Section 9.7) by which absorbed ultraviolet energy is accomodated within the molecule, which reacts
to produce the more energized enol form. In Step 2 the molecule reverts back to the
(14.7.2) more stable keto form, losing energy thermally in the process. The net result is that
energy is absorbed, the excited absorbing species reacts only with itself, then the energy is dissipated harmlessly as thermal energy, which does not cause additional reactions to occur.
The “tie-in strategy” has been proposed as a sensible approach to dealing with the kinds of global environmental problems discussed in this chapter. This approach was first enunciated in 1980. 11 It advocates taking measures consisting of “high- leverage actions” which are designed to prevent problems from occurring and which have substantial merit even if the major problems that they are designed to avoid do not materialize. An example is implementation of environmentally sound substitutes
for fossil fuels to lower atmospheric CO 2 output and prevent greenhouse warming. Even if it turns out that the greenhouse effect is exaggerated, such substitutes would save the earth from other kinds of environmental damage, such as disruption of land by strip mining coal or preventing oil spills from petroleum transport. Definite economic and political benefits would also accrue from lessened dependence on uncertain, volatile petroleum supplies. Increased energy efficiency would diminish both greenhouse gas and acid rain production, while lowering costs of production and reducing the need for expensive and environmentally disruptive new power plants. The implementation of these kinds of tie-in strategies requires some degree of incentive beyond normal market forces and, therefore, is opposed by some on ideological grounds. A good example is opposition to mandatory fuel mileage
standards for automobiles. However, to quote Schneider, 12 “a market that does not include the costs of environmental disruptions can hardly be called a free market.”