POISONS AND PRECARIOUS BALANCE : One Pollution May Protect Against Another

Hold on to your hats, or at least your sunglasses: Acid rain may be preventing global warming.

Sulfur dioxide, the power-plant byproduct that is the chief cause of acid rain, is colorless when it leaves the smokestack, but turns bright white as it interacts with the atmosphere. New research has raised the possibility that the whitening effect of sulfates from this pollution increases the albedo (reflectivity) of the Earth’s cloud layer, causing more solar energy to be mirrored back into space. This would cool the atmosphere somewhat.

Maybe it is no coincidence that during the very decades when artificial greenhouse gas emissions have dramatically increased without--so far at least--triggering a runaway world heat wave, sulfur emissions have skyrocketed too, keeping the planet’s temperature in a kind of zany equilibrium. But consider: Congress is finally hitching up its pants to do something about acid rain. Several pending legislative proposals, including one sponsored by President George Bush, call for sharp reductions. There’s no sign, however, of Washington preparing to face the music on the greenhouse effect. Slowing its advance would involve serious reductions in fossil fuel use coupled with other measures far more expensive and disruptive to the industrial world’s auto-oriented life styles than controlling sulfur dioxide. Thus without progress against global warming, progress against acid rain could actually backfire.

This possible relationship between sulfur and the greenhouse effect is unproved; it’s strictly theory and may turn out to be wrong. But it illustrates the strange interrelations that can spring up when we tamper with the vastness of nature.

The environment is not a machine but a living system. Like the body, it has some ability to adapt in response to chemical intrusions and, like the body, may even come to depend on substances that would otherwise be considered poisons. In the same manner that toxic pharmaceuticals are sometimes administered to counter the effects of disease microbes and other unwanted presences in the body, deliberate pollution may be sent chasing after the careless kind.

Currently, in several Scandinavian countries, lakes are being “limed”--bombed with tons of pulverized limestone--to control the pH caused by acid rain. There are proposals to do this in the United States. Better to have lakes flavored than acidic, one supposes, but who knows what effect the lime will have, in turn?

Another speculative theory on why global warming has been held in check is that, coming into the postwar industrial boom period, the world’s oceans were by coincidence relatively cool. Oceans are weather moderators: The enormous mass of water in the sea tends to “store” temperature differences the same way rocks are used to store heat or cold in solar homes. If the atmosphere is relatively cool for some period, the sea will tend to soak that up and remain cool for years or decades after the weather warms--moderating that warming downward. Ocean absorption of greenhouse heat may then have worked in opposition to global warming during recent decades.

This effect holds, however, only until the relative coolness of the sea is used up. The principal evidence that oceans may be warming somewhat is recent variations in El Nino and other major current systems: Ocean currents are driven partly by temperature gradients. If indeed the sea has been forestalling global warming, then we’re living on borrowed time--because even if in decades to come humanity brings its greenhouse gas emissions under control, by then the oceans will have become relatively warm and will for many years exert the side effect of steaming up an atmosphere that would otherwise cool.

Today the most important and scientifically irrefutable interplay of pollutants involves ozone. The public is continually being told that higher levels of ozone in smog is bad, really bad. At the same time the public is told that lower levels of ozone in the stratosphere is bad, really bad. Here’s the distinction.

Ozone is a special molecular form of oxygen. In nature it is found only in the stratosphere and the vicinity of lightning--but some pollutants, principally from cars and trucks, cause ozone artificially. Close to the ground, where people breathe it, ozone is a hazard because unlike normal oxygen, it degrades lung tissue. But high up in the stratosphere where it’s never inhaled, ozone is a safeguard of terrestrial life, because it screens solar and cosmic ultraviolet radiation far more effectively than normal oxygen. Such radiation can cause skin cancer, birth defects and other problems.

If the ozone being manufactured above our cities by smog pollutants could somehow be piped up to the stratosphere, two problems would be solved at once. Patent applications being accepted. Meanwhile, here’s the maddening part. Chloroflurocarbons (CFCs), the pollutants principally responsible for depleting the ozone layer, are mainly emitted in big cities--the same places where ozone is a health hazard. If only CFCs would attack the ozone in smog, another zany equilibrium might be established.

Unfortunately CFCs are not converted into anti-ozone agents until they drift up into the stratosphere and are chemically altered by solar and cosmic rays. Some chemists have even suggested modifying CFCs so that their transformation into ozone-eaters would occur in low-altitude air, creating a pollutant-based counterbalance to smog. Unfortunately this idea would have the side effect of filling urban air with chlorine, a powerful caustic. Instead, the United States and most Western nations have signed an agreement to cut CFC manufacture 50% by the turn of the century, and Bush has endorsed upgrading the agreement into an outright ban. This issue may become moot in the United States because E.I. du Pont de Nemours & Co., the principal manufacturer of CFCs, has announced it will voluntarily phase out the compounds.

Du Pont made this commitment in part because its chemists invented a new substance that can replace CFCs in air conditioners and refrigeration equipment, the leading CFC use. Unfortunately Du Pont’s creation has a problematic side effect. It is less efficient than CFCs--meaning cars with air conditioners operating will burn more gasoline, while municipal power plants will consume more coal and other fuels to generate more electricity for cooling homes and office buildings, increasing the emission of gases with greenhouse effects. And, as the climate warms, it means even more fuel use for air conditioning, which in turn would amplify the greenhouse effect, which in turn . . . .

As for zany side effects: How about a few good words for smog? Filthy air is not without its compensations. Studies are beginning to show that people who live in such badly polluted cities as Los Angeles have lower rates of skin cancer, blindness and certain birth defects than those who live healthful lives on the farm or the pristine outback--because cosmic rays can’t get through the smog any more than anything else can. This “portable ozone layer” effect, assuming it can be upheld by further research, would suggest that as stratospheric ozone depletion advances it may actually become healthier to tan yourself on Venice Beach, safely snuggled under the friendly Los Angeles smog dome, than in some dangerously clean place such as Hawaii or Australia. Assuming, that is, you bring your own breathing apparatus.

Another equilibrium question concerns deforestation. Most ecologists believe that it’s bad to cut or burn forests because trees, like any vegetation, subtract carbon dioxide from the atmosphere. The typical ecologist would say, in fact, that few things are better for the Earth and its inhabitants than preserving the maximum acreage of forest. Recent research suggests, however, that under some circumstances trees are a source of hydrocarbon pollutants that cause smog. How it pains to think that Ronald Reagan’s “killer trees” wisecrack might have been right. Or at least, like so many of his anecdotes, sorta kinda right.

There’s even a line of thought holding that logging forests is great for the environment, assuming each cleared area is promptly replanted. Young, growing trees withdraw carbon dioxide faster than mature ones. Moreover, it is possible that wooded stands are a net minus for the greenhouse effect compared to, say, using the same land for farming. Forests, being dark in color, have a low albedo, and so may contribute to the retention of solar warmth. Ideally one zany arrangement for combating global warming would call for forests to be continuously logged and replanted with some type of genetically engineered tree that grows frantically fast and has white leaves, making the brave new forest look, from space, like a giant daisy.

There’s no indication that radon prevents heart disease, that dioxin contamination is what is stopping the killer bees or any such link that would make pollution actually sound good. But as the 22nd-Century scientist said of Woody Allen’s request for sprouts and carrot juice in the movie “Sleeper”--”Didn’t they know about hot fudge back then? The benefits of deep-fat frying?”--the damage done by pollution may not stop at the obvious. There may be many more undiscovered--and unwanted--side effects.