A pilot programme to measure the South Asian outflow of ozone depleting substances and greenhouse gases

We will develop a programme to measure greenhouse gases (GHGs) and ozone depleting substances (ODSs) from the Maldives Climate Observatory-Hanimaadhoo (MCOH), which intercepts the outflow of polluted air from South Asia. South Asia is an important region of the world that, to date, has never had routine measurement of many major trace gases such as the halocarbons that will be measured here. We will collect air in flasks and analyse them for the full suite of ~50 synthetic halocarbon gases measured in the Advanced Global Atmospheric Gases Experiment (AGAGE). We will estimate South Asia's emissions of the chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs) and hydrofluorocarbons (HFCs), the compounds regulated by the international Montreal Protocol on Substances that Deplete the Ozone Layer. CFCs are potent ODSs that were used widely around the world for refrigeration, air-conditioning and foam blowing. Production and use of CFCs have been banned globally under the Montreal Protocol. In response, industries switched to replacement compounds known as HCFCs. While less damaging to the ozone layer than CFCs, HCFCs still have ozone destruction properties. Thus, HCFCs were subsequently regulated under the Montreal Protocol but developing countries are still permitted to emit HCFCs with a gradual phase-out. The replacements for HCFCs are HFCs, which do not deplete ozone but are potent GHGs. To reduce their impact on climate, the Montreal Protocol set a phase-down schedule for HFC production and use - with cuts in many countries not beginning until 2024. Our study will allow us to determine South Asia's emissions of CFCs, HCFCs and HFCs over 2021-2022 and to assess the suitability of MCOH in monitoring the outflow of halocarbon pollutants from South Asia so that long-term measurements can be implemented at this site.