Ozone Hole on the Rebound

"Ozone in the upper atmosphere protects life on Earth from harmful solar rays, and a thinning on ozone--even total depletion in some areas--has been a concern since the 1970s," said study coauthor Betsy Weatherhead of the NOAA Earth System Research Laboratory in Boulder, Colo.

Ozone--which is three oxygen atoms bonded together--is constantly being created, broken down, and circulated in the atmosphere, and as pollutants filter out of the atmosphere, the layer naturally rebuilds. Data from NOAA, NASA, and a global monitoring network show that atmospheric levels of chlorine have leveled off and ozone loss is clearly leveling off, too.

The researchers showed that the ozone layer is recovering "in the right seasons, in the right latitudes, and at the right altitudes." The study is the first to show that the positive changes in the ozone layer are in general agreement with what is expected due to the reduced chlorine emissions, and is a success story for the 1987 international agreement to control ozone-depleting chemicals in the atmosphere.

Weatherhead cautioned, however, that these are the early stages of recovery, and it is difficult to say whether the recent changes will be reflected in the long-term.

"We may still see very low ozone levels in the next few years, but the general tendency we're observing is that the atmosphere is starting to heal," said Weatherhead.

Despite these results, the ozone remains at below-normal levels at all latitudes, and ultra-violet (UV) rays from the sun are still higher than they should be, Weatherhead said. People should continue to protect themselves from UV rays when they are outdoors.

--Bjorn Carey

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Credit: NOAA