Preprints
https://doi.org/10.5194/egusphere-2024-1289
https://doi.org/10.5194/egusphere-2024-1289
13 May 2024
 | 13 May 2024
Status: this preprint is open for discussion and under review for Atmospheric Chemistry and Physics (ACP).

The return to 1980 stratospheric halogen levels: A moving target in ozone assessments from 2006 to 2022

Megan Lickley, John S. Daniel, Laura A. McBride, Ross J. Salawitch, and Guus Velders

Abstract. The international scientific assessment of ozone depletion is prepared every four years to support decisions made by the Parties to the Montreal Protocol. In each assessment an outlook of ozone recovery time is provided. The year when equivalent effective stratospheric chlorine (EESC) returns to the level found in 1980 is an important metric for the recovery of the ozone layer. Over the past five assessments, the expected date for the return of EESC to the 1980 level, for mid-latitudes, has been delayed, from year 2049 in the 2006 assessment to 2066 in the 2022 assessment, which represents a delay of 17 years over a 16-year assessment period. Here, we quantify the primary drivers that have delayed the expected EESC recovery date between each of these assessments. We find that by using identical EESC formulations the delay between the 2006 and 2022 assessment’s expected return of EESC to 1980 levels is shortened to 12.6 years. Of this delay, bank calculation methods account for ~4 years, changes in the assumed atmospheric lifetime for certain ODSs account for ~3.5 years, an under-estimate of the emission of CCl4 accounts for ~3 years, and updated historical mole fraction estimates of ODSs account for ~1 year. Since some of the underlying causes of these delays are amenable to future controls (e.g. capture of ODSs from banks and limitations on future feedstock emissions), it is important to understand the reasons for the delays in expected recovery date of stratospheric halogens.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Megan Lickley, John S. Daniel, Laura A. McBride, Ross J. Salawitch, and Guus Velders

Status: open (until 24 Jun 2024)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
Megan Lickley, John S. Daniel, Laura A. McBride, Ross J. Salawitch, and Guus Velders
Megan Lickley, John S. Daniel, Laura A. McBride, Ross J. Salawitch, and Guus Velders

Viewed

Total article views: 179 (including HTML, PDF, and XML)
HTML PDF XML Total Supplement BibTeX EndNote
112 64 3 179 7 1 2
  • HTML: 112
  • PDF: 64
  • XML: 3
  • Total: 179
  • Supplement: 7
  • BibTeX: 1
  • EndNote: 2
Views and downloads (calculated since 13 May 2024)
Cumulative views and downloads (calculated since 13 May 2024)

Viewed (geographical distribution)

Total article views: 175 (including HTML, PDF, and XML) Thereof 175 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Latest update: 19 May 2024
Download
Short summary
The expected ozone recovery date has been delayed by 17 years between the 2006 and 2022 international scientific assessments of ozone depletion. We quantify the primary drivers of this delay. Changes in the metric used to estimate ozone recovery explains ~5 years of this delay. Of the remaining 12 years, changes in estimated banks, atmospheric lifetimes, and emission projections explain 4, 3.5 and 3 years of this delay, respectively.