Fingerprints of the cosmic ray driven mechanism of the ozone hole

There is long research interest in electron-induced reactions of halogenated molecules. It has been two decades since the cosmic-ray (CR) driven electron-induced reaction (CRE) mechanism for the ozone hole formation was proposed. The derived CRE equation with the stratospheric equivalent chlorine level and CR intensity as the only two variables has well reproduced the observed data of stratospheric O3 and temperatures over the past 40 years. The CRE predictions of 11-year cyclic variations of the Antarctic O3 hole and associated stratospheric cooling have also been well confirmed. Measured altitude profiles of the ozone and temperatures in Antarctic ozone holes provide convincing fingerprints of the CRE mechanism. A quantitative estimate indicates that the CRE-produced Cl atoms could completely deplete or even overkill the ozone in the CR-peak polar stratospheric region, consistent with the observed altitude profiles of the severest Antarctic ozone holes. After removing the natural CR effect, the hidden recovery in the Antarctic O3 hole since ∼1995 is clearly discovered, while the recovery of O3 loss at mid-latitudes is being delayed by ≥10 years. These results have provided strong evidence of the CRE mechanism. If the CR intensity keeps the current rising trend, the Antarctic O3 hole will return to the 1980 level by ∼2060, while the returning of the O3 layer at mid-latitudes to the 1980 level will largely be delayed or will not even occur by the end of this century. The results strongly indicate that the CRE mechanism must be considered as a key factor in evaluating the O3 hole.