09 Feb 2023
 | 09 Feb 2023
Status: this preprint is currently under review for the journal ACP.

A Method for Calculating Offsets to Ozone Depletion and Climate Impacts of Ozone-Depleting Substances

Gabrielle B. Dreyfus, Stephen A. Montzka, Stephen O. Andersen, and Richard Ferris

Abstract. By phasing out production and consumption of most ozone depleting substances (ODSs), the Montreal Protocol on Substances that Deplete the Ozone Layer (Montreal Protocol) has avoided consequences of increased ultraviolet (UV) radiation, and it will restore stratospheric ozone to pre-1980 conditions by mid-century, assuming compliance with the phaseout. However, several studies have documented an unexpected increase in emissions and unreported production of trichlorofluoromethane (CFC-11) and other ODSs that occurred after 2012 despite production phaseouts under the Montreal Protocol. Furthermore, because most ODSs are powerful greenhouse gases there are significant climate protection benefits in collecting and destroying the substantial quantities of historically allowed products under the Montreal Protocol that are contained in existing equipment and products and referred to as ODS “banks”. Here we present a framework for considering offsets to ozone depletion, climate forcing, and other environmental impacts arising from this or other occurrences of unexpected emissions and unreported production of Montreal Protocol controlled substances. We also show how this methodology could be applied to the destruction of banks of controlled ODSs and GHGs, or to halon or other production allowed under a Montreal Protocol Essential Use Exemption or emergency exemption. Further, we explore a range of potential actions that could offset the ozone depletion, climate, and other environmental impacts arising from instances of unexpected emissions or unreported production should Montreal Protocol Parties agree require remedial action.

Gabrielle B. Dreyfus et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2023-53', Anonymous Referee #1, 15 Mar 2023
    • AC1: 'Reply on RC1', gabrielle Dreyfus, 11 Aug 2023
  • RC2: 'Comment on acp-2023-53', Anonymous Referee #2, 05 Apr 2023
    • AC2: 'Reply on RC2', gabrielle Dreyfus, 11 Aug 2023

Gabrielle B. Dreyfus et al.

Gabrielle B. Dreyfus et al.


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Short summary
The Montreal Protocol has put the ozone layer on a path to recovery by phasing out 99 % of banned ozone-damaging substances. Most of these banned substances are also potent greenhouse gases. Atmospheric monitoring has detected unexpected increases in emissions in several of these banned substances. Here we show how damage to ozone, climate and health can be quantified for these emissions and offset by preventing the equivalent emissions of ozone-damaging substances by destroying existing stocks.