for ODSs from the Earth’s surface (largely in the Northern Hemisphere) to the stratosphere at Southern Hemisphere mid- and Antarctic latitudes. Arrows indicate dates when the mid-latitude and Antarctic stratospheres return to pre-1980s levels of EESC, and approximately pre-ozone hole levels of stratospheric ozone. In response to the need to easily convey information to the general public about the levels of chemicals in the atmosphere, and when might the ozone hole recover, NOAA has developed the Ozone Depleting Gas Index (ODGI) (Hofmann and Montzka, 2009; and recent updates see ). The index neatly describes the state of the atmosphere, in relation to stratospheric halogen (chlorine plus bromine) levels, and is based on atmospheric measurements of ODSs. The index has two components, one relevant for ozone-depleting chemicals and the ozone hole over Antarctica (the ODGI-A), and one relevant for mid- (the ODGI-ML). Figure 12 shows the CSIRO version of the ODGI-ML and ODGI-A indices derived from global AGAGE data including data from Cape Grim. Based on data up to 2017, the ODGI-A and indices have declined by 21% and 43% respectively since their peak values in 2000 and 1998 respectively, indicating that the atmosphere in 2017 is 21% and 43% along the way toward a halogen level that should allow an ozone-hole free Antarctic stratosphere and a (pre-1980s) ozone layer at ‘normal’ The CSIRO version of the ODGI uses ODS fractional release factors from Newman et al. (2007). Figure 12. ODGI-A and ODGI-ML indices (Hofmann and Montzka, 2009) derived from AGAGE ODS data using ODS fractional release factors from Newman et al. (2007).
for ODSs from the Earth’s surface (largely in the Northern Hemisphere) to the stratosphere at Southern Hemisphere mid- and Antarctic latitudes. Arrows indicate dates when the mid-latitude and Antarctic stratospheres return to pre-1980s levels of EESC, and approximately pre-ozone hole levels of stratospheric ozone. In response to the need to easily convey information to the general public about the levels of chemicals in the atmosphere, and when might the ozone hole recover, NOAA has developed the Ozone Depleting Gas Index (ODGI) (Hofmann and Montzka, 2009; and recent updates see ). The index neatly describes the state of the atmosphere, in relation to stratospheric halogen (chlorine plus bromine) levels, and is based on atmospheric measurements of ODSs. The index has two components, one relevant for ozone-depleting chemicals and the ozone hole over Antarctica (the ODGI-A), and one relevant for (the ODGI-ML). Figure 12 shows the CSIRO version of the ODGI-ML and ODGI-A indices derived from global AGAGE data including data from Cape Grim. Based on data up to 2017, the ODGI-A and indices have declined by 21% and 43% respectively since their peak values in 2000 and 1998 respectively, indicating that the atmosphere in 2017 is 21% and 43% along the way toward a halogen level that should allow an ozone-hole free Antarctic stratosphere and a ‘normal’ (pre-1980s) ozone layer at The CSIRO version of the ODGI uses ODS fractional release factors from Newman et al. (2007). Figure 12. ODGI-A and ODGI-ML indices (Hofmann and Montzka, 2009) derived from AGAGE ODS data using ODS fractional release factors from Newman et al. (2007). mid-
2017-ozone-summary-report.docx