Investigating HALocarbon impacts on the global Environment (InHALE)

With the Kigali Amendment coming into force in 2019, the Montreal Protocol on Substances that Deplete the Ozone Layer has entered a major new phase in which the production and use of hydrofluorocarbons (HFCs) will be controlled in most major economies. This landmark achievement will cement the Protocol's already-substantial benefits to climate. However, recent scientific advances have identified challenges that threaten to limit its future success, including the re-emergence of production of ozone-depleting halocarbons thought to be phased-out, rapid growth of ozone-depleting compounds not controlled under the Protocol, and the potential for damaging impacts of halocarbon degradation products. This proposal tackles the most urgent scientific issues relating to halocarbons relevant to the Montreal Protocol to better determine their atmospheric abundances, emissions, and environmental impacts. By combining atmospheric measurements, targeted laboratory experiments and advanced numerical modelling we will: 1) expand atmospheric measurement coverage, in terms of number of locations and number of compounds, with the aim of better understanding the global distribution of halocarbon emissions and identifying and quantifying previously unknown atmospheric trends, 2) improve our understanding of the relationship between production (the quantity controlled under the Protocol), "banks" of halocarbons stored in buildings and products, and emissions to the atmosphere, by combining industry models and atmospheric data, 3) determine recent and likely future trends of unregulated, short-lived halocarbons, and implications for the timescale of recovery of the ozone layer, 4) explore the complex atmospheric chemistry of halocarbons that are proposed as replacements for HFCs, and determine whether breakdown products have the potential to contribute to climate change or lead to other negative environmental consequences, 5) better quantify the influence on climate of halocarbons and refine the climate- and ozone-depletion-related metrics used to compare the effects of halocarbons in international agreements and in the design of possible mitigation strategies. This work will be carried out by a consortium of leaders in the field of halocarbon research, who have an extensive track record of contributing to Montreal Protocol bodies and the Intergovernmental Panel on Climate Change, which will ensure lasting impact of the new developments that will be made.