Global Warming is Changing the Path of the Arctic Ozone Recovery
NASA AMES Research
Polar stratospheric cloud (PSC) sightings date back to the nineteen century and up to only a few decades ago they were primarily noted and admired for their natural beauty that sporadically filled up the skies over the poles with colorful glows throughout the winter and early spring. Soon after the discovery of the springtime Antarctic "ozone hole", chlorofluorocarbons (CFCs) along with naturally occurring PSCs were implicated to play important roles in ozone destruction. It was hypothesized and later proven that PSCs promote formation of active chlorine, originally derived from man-made emission of CFCs, that catalytically destroys ozone molecules.
Satellites and ground-based observations indicate that CFC emissions are declining in the atmosphere and accordingly it was expected that the ozone layer should rapidly recover, responding to international agreements that ban CFC emissions. However, greenhouse gases, which provide warming at the Earth's surface, lead to cooling in the stratosphere where the ozone layer is located. Cooling in the stratosphere increases PSC coverage, prolonging the cycle of ozone destruction. Thus global warming has the potential to significantly slow down the ozone recovery, particularly over the Arctic region, where ozone depletion is highly sensitive to temperature variations. In fact if the observed cooling trends (2 K per decade) in the stratosphere continue, an "ozone hole" could develop over populated areas in the Arctic in the next few decades prior to its full recovery later in the century.