Things are looking up for ozone hole - UN weather org

This screen grab taken from footage taken by Japan's Himawari-8 satellite shows the volcanic eruption that provoked a tsunami in Tonga. Photo: Handout / National Institute of Information and Communications Technology / AFP

The UN's weather arm says the ozone layer is on track to long-term recovery.

The World Meteorological Organisation (WMO) has issued its annual WMO Ozone and UV Bulletin, which looks at the role of meteorological conditions and a major volcanic eruption on the Antarctic ozone hole in 2023, while also highlighting growing evidence that the ozone layer is on track to long-term recovery.

The report said when compared to 2022, October and November of 2023 saw significantly less ozone loss.

"The important eruption of the Hunga Tonga-Hunga Ha'apai volcano on 15 January 2022 increased the amount of water vapour in the stratosphere," the report said.

It said recent research indicates that in the lower Antarctic stratosphere, this excess water vapour has had a limited effect on the rate of ozone destruction, which is triggered by sunlight and the addition of certain chemical substances.

But "such excess water vapour did enhance depletion in the middle and upper layers, particularly near the edge of the Antarctic stratospheric vortex".

The eruption resulted in some ozone transport changes.

"In the southern hemisphere, the higher mid-latitude values of 2023 ended several years of low total ozone columns caused in part by the large Australian wildfires in 2020/2021 and by ozone transport changes induced by excess water vapour from the Hunga Tonga-Hunga Ha'apai volcanic eruption in 2022," the report said.

Research found the vapour from the eruption reached heights of up to 55 kilometres and depleted 5 percent of the ozone layer over the tropical south-western Pacific and Indian Ocean regions in one week.

The WMO report said total ozone levels over the Antarctic were lower than average between January and July 2023, which led to an earlier detection of the ozone hole, based on normal detection thresholds.

"Total ozone column levels were impacted into the Antarctic spring due to these low starting levels. This could be related to enhanced mid-latitude stratospheric ozone depletion from the Hunga Tonga-Hunga Ha'apai eruption."

But things are looking up - the report said if current policies remain in place, the ozone layer is expected to recover to 1980 values (before the appearance of the ozone hole) by around 2066 over the Antarctic; by 2045 over the Arctic; and by 2040 for the rest of the world.