2011 News & Events

When Will We See the First Signs that the Antarctic Ozone Hole is Beginning Its Recovery?

7 October 2011

researchers with balloon
Scientists release a balloon that will carry an ozone-measuring instrument into the stratospheric ozone layer above the South Pole, September 2011. Photo: Christy Schultz, NOAA Corps

A new analysis by scientists at ESRL suggests that between about 2017 and 2021, the longtime atmospheric data record at the South Pole might show initial signs of recovery of the annual Antarctic ozone hole.

The study, "An assessment of changing ozone loss rates at South Pole: Twenty-five years of ozonesonde measurements," was published online in the Journal of Geophysical Research at the end of September. Scientists from CSD and GMD authored the paper on the analysis, led by Birgit Hassler of CSD and the Cooperative Institute for Research in Environmental Sciences (CIRES).

GMD researchers have been tracking ozone levels high in the Antarctic atmosphere above the South Pole for 25 years, keeping an eye on the annual springtime formation – and breakdown – of the ozone hole.

The ozone layer protects Earth from some damaging incoming solar radiation; an ozone hole means more incoming radiation can hit the surface, elevating the risk of skin cancer, crop damage, and other environmental impacts.

The research team analyzed the rates at which springtime chemical reactions ate away at ozone above the South Pole during the last 25 years.

The team related those "ozone loss rates" to the atmosphere's levels of ozone-depleting chemicals, which are declining in abundance because of the international Montreal Protocol agreement to protect the ozone layer.

Projecting that relationship into the future, the research team calculated that between 2017 and 2021, the South Pole data will show that ozone is not being lost as quickly during the spring – an early sign that the Antarctic ozone hole is healing.

Hassler, B.1,2, J. S. Daniel2, B. J. Johnson3, S. Solomon2,4, and S. J. Oltmans3, An assessment of changing ozone loss rates at South Pole: Twenty-five years of ozonesonde measurements, Journal of Geophysical Research, doi:10.1029/2011JD016353, 2011.

  1. Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder
  2. Chemical Sciences Division, Earth System Research Laboratory, National Oceanic and Atmospheric Administration
  3. Global Monitoring Division, Earth System Research Laboratory, National Oceanic and Atmospheric Administration
  4. Department of Atmospheric and Oceanic Science, University of Colorado, Boulder

In 2010, 25 years of regular, year-round ozone soundings at South Pole station, Antarctica, were completed. These measurements provide unique information about the seasonality, trends, and variability of ozone depletion in the polar stratosphere at high vertical resolution. Here, we focus on the observed loss rates, and their changes since the measurement series began. The fastest loss rates occur between the end of August and end of September between 50 hPa and 30 hPa. Loss rates at these pressure levels increased by approximately 40% from the late 1980s to the late 1990s and have remained stable within estimated uncertainties since then. To estimate the time frame when a reduction in ozone loss rates will be observable outside the range of dynamical variability at the South Pole, we scale the estimated loss rates to the future projected concentrations of equivalent effective stratospheric chlorine (EESC). If a linear relationship between ozone loss rates and EESC is assumed, we project that a change in lower stratospheric ozone loss rates at South Pole station will be first detectable in the 2017-2021 time period.