Watch the Antarctic ozone hole grow and shrink before your eyes.

Good news! The average area covered by the Antarctic ozone hole this year, NASA has announced, was the second smallest it's been in the last 20. But bad news! That's partly because of climate change. Scientists attribute the shift to warmer temperatures in the Antarctic lower stratosphere.

The GIF above encompasses nearly four months' worth of atmospheric data gathered by National Oceanic and Atmospheric Administration satellites. (The purples and blues indicate a lack of ozone; the yellows and reds indicated the presence of more ozone.) On September 22, the ozone hole over Antarctica reached its maximum size, covering 8.2 million square miles -- or the area, NASA points out, of the United States, Canada, and Mexico combined.

Here, in non-GIF form, are the day-by-day images of the Antarctic ozone hole for the month of October. You can see the blue decrease ever so slightly as the days go by.

The shrinking Antarctic ozone hole, NASA has said before, represents "a signature environmental success story." The Montreal Protocol, which regulates ozone-depleting substances, seems to be doing its job. As two data points, compare the 8.2 million-mile size of the hole on September 22, 2012 to the size of the hole as it was on September 6, 2000: 11.5 million square miles.

For 2012, for another comparison, the average size of the ozone hole was 6.9 million square miles -- about the size of South America. So, you know: improvement.

Scientists expect that the ozone layer will once again reach full strength; and they expect -- if the Montreal Protocol stays in place -- that the ozone hole itself will one day be completely eliminated. That's the good news. The bad news? They don't expect the hole to be mended until 2065.

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