The ozone "hole" over Antartica reached its southern springtime peak in September, according to researchers with the National Oceanic and Atmospheric Administration. Measurements there indicated the size of the gap in the layer of the planet's atmosphere that protects us from dangerous ultraviolet radiation was the 10th largest on record.

That sounds bad, but the data suggest that the hole has actually begun to shrink thanks to international restrictions in the early 1990s on the production and sale of products containing chlorofluorocarbons (CFCs), mostly as propellants and refrigerants. The chemicals were discovered to be responsible for high-altitude chemical reactions in the coldest places on Earth that were destroying ozone molecules. Man-made ozone is a pollutant at ground level, but naturally occurring ozone high in the atmosphere acts as a shield against harmful solar radiation. 

The other piece of the measurement is the amount of ozone in a vertical column of air over South Pole Station. That's measured in something called Dobson Units.

The least amount of protective ozone ever measured there was 89 Dobson Units, in 1993. This September, the lowest reading was 98 Dobson Units. That's the seventh lowest on record, but an improvement.

The chart at right shows the average Dobson readings for the last half of October each year. You can see that the depletion appears to have ended during the 1990s, and ozone readings have stabilized and perhaps ticked up a notch.

But the progress is painfully slow. At this rate, the ozone hole won't return to normal until the 2060s. By then, lots of us (including me) will be dead. But our children and grandchildren will be around, and I hope they throw a big party and thank their ancestors for thinking for the long-term (for a change).

You can read more about this year's measurements here.