WASHINGTON (AP) — Warm air at high altitudes this September and October helped shrink the man-made ozone hole near the South Pole ever so slightly, scientists say.

The hole is an area in the atmosphere with low ozone concentrations. It is normally is at its biggest this time of year. NASA says on average it covered 8.1 million square miles this season. That’s 6 percent smaller than the average since 1990.