2017-10-24: Antarctic Ozone Hole decreased by 20%

The Antarctic Ozone Hole that forms over Antarctica ever year during springtime is continuing to heal. Since about the year 2000 its ozone depletion has decreased by approximately 20%. Likely this is mostly due to international agreements on the protection of the ozone layer. Such are the findings of a recently published new research paper by KNMI. First signs of global recovery of the ozone layer had already been reported before.

The Ozone Hole is an icon with regard to the human impact on climate and the environment. The rapid thinning of the ozone layer over Antarctic led in the 1980s to far reaching international agreements for banning the industrial production and emissions of ozone depleting substances (cooling agents, propellants in spray cans).

From there onwards scientists have been looking for signs of recovery in observations. Due to large natural year-to-year variability in the amount of ozone depletion it has been proven to be far from easy to unequivocally isolate the expected recovery, let alone that changes can be attributed to the policy measures taken. Furthermore, climate change does also affect the recovery of the ozone layer and healing of the Antarctic Ozone Hole.

The largest complication is associated with natural variability. The seasonal temperatures in the ozone layer varies a little bit from year to year similar to our seasons, like one winter will a little bit colder or warmer than the next, even though winters are always cold. Chemical ozone destruction is very sensitive to these relatively small temperature anomalies, leading to occasional years where, like this year (2017), ozone depletion is strongly reduced (figure 1).

The new scientific publication by KNMI in the Journal of Geophysical research addresses the question what is the best method to establish healing of the Ozone Hole. Based on more than 35 years of daily satellite measurements the authors conclude that the ozone hole has already healed by approximately 20%, which is in agreement with the observed decrease in the amount of ozone depleting substances and with model simulations that indicate how much the thickness of the ozone layer in the Ozone Hole should have increased. It has yet to be unequivocally established that the observed increase in its entirety can be attributed to the decrease in ozone depleting substances, or that there still exist other effects that have not been well characterized. This likely will take quite a number of time and more years so that the measurements time series will be much longer. But a consistent picture is emerging, and it is clear how to continue monitoring the developments from year to year. KNMI contributes to this important issue by providing satellite observations of the ozone layer. Ozone data from the TROPOMI satellite that was successfully launched on 13 October 2017 are an essential contribution to this.

Read the full article here.
More background information can be found here.
Annual decrease in ozone over Antarctic on 14 September for each year since 1979 based on MSR reanalysis data. In red years with strongly reduced ozone depletion due to natural variability.