11 May 2022
New research published in Atmospheric Chemistry and Physics projects future emissions of hydrofluorocarbons (HFCs), a class of potent greenhouse gases, based on recent trends and compliance with current policies. As substitutes for ozone-depleting substances, the emissions of HFCs have increased substantially over the past two decades as a result of the phaseout of ozone-depleting substances under the Montreal Protocol. Due to the growing climate impact of HFCs, the Kigali Amendment to the Montreal Protocol has scheduled a phase-down of their future production and consumption. The results show that total CO2 equivalent global HFC emissions derived from NOAA observations continue to increase through 2019, but are about 20% lower than previously projected for 2017-2019, mainly because of the lower global emissions of HFC-143a, which is one of the longer-lived HFCs in use today. Current policies reduce projected emissions in 2050 from 4.0-5.3 GtCO2eq.yr-1 in the absence of controls to 1.9-3.6 GtCO2eq.yr-1, and the added provisions of the Kigali Amendment reduce the projected emissions further to 0.9-1.0 GtCO2eq.yr-1. Without any controls, HFC emissions are projected to contribute 0.28-0.44 °C to global surface warming by 2100, compared to a contribution of about 0.04 °C by 2100 with Kigali Amendment controls.
This study is designed to give policymakers quantitative feedback on the future climate benefits anticipated from the Kigali Amendment, which will guide the Parties to the Montreal Protocol to decide if existing controls in the Protocol need revision, depending on the climate outcomes that they hope to achieve through the Montreal Protocol.
Velders, G.J.M., J.S. Daniel, S.A. Montzka, I. Vimont, M. Rigby, P.B. Krummel, J. Muhle, S. O'Doherty, R.G. Prinn, R.F. Weiss, and D. Young, Projections of hydrofluorocarbon (HFC) emissions and the resulting global warming based on recent trends in observed abundances and current policies, Atmospheric Chemistry and Physics, doi:10.5194/acp-22-6087-2022, 2022.
The emissions of hydrofluorocarbons (HFCs) have increased significantly in the past 2 decades, primarily as a result of the phaseout of ozone-depleting substances under the Montreal Protocol and the use of HFCs as their replacements. In 2015, large increases were projected in HFC use and emissions in this century in the absence of regulations, contributing up to 0.5 °C to global surface warming by 2100. In 2019, the Kigali Amendment to the Montreal Protocol came into force with the goal of limiting the use of HFCs globally, and currently, regulations to limit the use of HFCs are in effect in several countries. Here, we analyze trends in HFC emissions inferred from observations of atmospheric abundances and compare them with previous projections. Total CO2 eq. inferred HFC emissions continue to increase through 2019 (to about 0.8 GtCO2eq.yr-1) but are about 20% lower than previously projected for 2017-2019, mainly because of the lower global emissions of HFC-143a. This indicates that HFCs are used much less in industrial and commercial refrigeration (ICR) applications than previously projected. This is supported by data reported by the developed countries and the lower reported consumption of HFC-143a in China. Because this time period preceded the beginning of the Kigali provisions, this reduction cannot be linked directly to the provisions of the Kigali Amendment. However, it could indicate that companies transitioned away from the HFC-143a with its high global warming potential (GWP) for ICR applications in anticipation of national or global mandates. There are two new HFC scenarios developed based (1) on current trends in HFC use and Kigali-independent (K-I) control policies currently existing in several countries and (2) current HFC trends and compliance with the Kigali Amendment (KA-2022). These current policies reduce projected emissions in 2050 from the previously calculated 4.0-5.3 GtCO2eq.yr-1 to 1.9-3.6 GtCO2eq.yr-1. The added provisions of the Kigali Amendment are projected to reduce the emissions further to 0.9-1.0 GtCO2eq.yr-1 in 2050. Without any controls, projections suggest a HFC contribution of 0.28-0.44 °C to global surface warming by 2100, compared to a temperature contribution of 0.14-0.31 °C that is projected considering the national K-I policies current in place. Warming from HFCs is additionally limited by the Kigali Amendment controls to a contribution of about 0.04 °C by 2100.