WASHINGTON — 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?