Shrinking ozone hole (IMAGE) University of Colorado at Boulder Caption The 2019 ozone hole reached a peak extent of 6.3 million square miles on September 8, 2019, the lowest maximum observed in decades. This NASA visualization depicts ozone concentrations in Dobson Units, the standard measure for stratospheric ozone. Credit NASA Usage Restrictions Credit: NASA License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.