To the editor:

A history lesson might be useful now, and give some cause for celebration.

In 1973, two University of California-Irvine scientists began studying the ozone layer, which protects us from harmful solar UV radiation, a prime cause of cataracts and skin cancer. They discovered that chlorofluorocarbons (CFCs) could rise to the stratosphere and break down, releasing chlorine that should destroy ozone. The National Academy of Sciences said that it sounded reasonable, but the chair of DuPont (who made CFCs) called it “a science fiction tale … a load of rubbish … utter nonsense.”

In 1985 a British team found out that the depletion was actually happening, making a large ozone hole in the Antarctic. The effects are worldwide. Still, industry argued that the science was too uncertain to justify any action. In 1987 and 1992 worldwide agreements (the Montreal Protocol), including the U.S., were made to stop manufacturing CFCs. Things got worse as stocks of CFCs were used up, and then leveled off.

This year the ozone layer began to heal itself. Satellite measurements of CFC byproducts in the upper atmosphere verified that it was beginning to drop, even a little sooner than was predicted. Don’t throw out your sunscreen, because it will take most of this century for things to return to 1950s levels. We are using new kinds of refrigerants now.

There’s a lesson here about what we can accomplish when we pay attention to the science and act on it instead of going into denial.