[In Depth] CFC bans pay off as Antarctic ozone layer starts to mend
Ever since its discovery in 1985, the springtime ozone hole over Antarctica has been an insistent reminder of humankind's ability to cause environmental harm. But the wound has begun to heal: There is now evidence that the hole is shrinking. The 1987 Montreal Protocol phased out ozone-destroying chemicals. And measurements have shown that atmospheric concentrations of those chemicals are declining. Now, researchers have found evidence of the intended consequence: a less holy ozone layer. Using satellites, ground-based instruments, and ozone-measuring weather balloons, they showed that since 2000, the September hole shrunk by 4 million square kilometers—an area bigger than India. An extra challenge was demonstrating that the shrinkage was due to the drop in chemicals. Using a 3D atmospheric model, the researchers separated the effect of the chemicals from those of weather and volcanic emissions, which can also destroy ozone. The model helped explain anomalously large ozone holes like the...