The Assessment documents the advances in scientific understanding regarding protection of the stratospheric ozone layer and climate from the production and consumption of ozone-depleting substances (ODSs) and their replacements. For HFCs, increases in atmospheric abundances are similar to those projected in the baseline scenario of the 2014 Assessment and currently amount to about 1.5% of total emissions from all long-lived greenhouse gases as carbon dioxide-equivalent emissions. Radiative forcing from HFCs amounts to 1% (0.03 W m-2) of the 3 W m-2 supplied by all long-lived greenhouse gases (GHGs). The Kigali Amendment is projected to reduce future global average warming in 2100 due to HFCs from a baseline of 0.3-0.5 °C to less than 0.1 °C. HFC emissions are projected to peak before 2040 and decline to less than 1 GtCO2-eq yr−1 by 2100, similar to the emissions in 2016 (0.88 GtCO2-eq yr−1).
Improvements in energy efficiency in refrigeration and air-conditioning equipment during the transition to low-GWP alternative refrigerants can potentially double the climate benefits of the HFC phasedown of the Kigali Amendment. The conversion from equipment using HFC refrigerants with high GWPs to refrigerants with lower GWPs, which will most likely result from the Kigali Amendment, provides an opportunity to consider other technological improvements that offer additional climate benefits. The use of a refrigerant with a lower GWP than the currently-used HFCs offers the opportunity to redesign equipment and improve its energy efficiency.
Only marginal increases are projected for CO2-eq emissions of the low-GWP alternatives, despite substantial projected increases in their emission mass. The figure taken from the SAP Executive Summary shows historical and projected emissions from ODSs,
HFCs (excluding HFC-23), and HFC alternatives (low-GWP alternatives), assuming full compliance with the provisions of the Montreal Protocol, including the Kigali Amendment. Also shown are projections for low-GWP alternatives. Note that the values for low-GWP alternatives in the bottom panels (yellow lines) are sufficiently small that they require enlargement to be visible.
Source World Meteorological Organization Global Ozone Research and Monitoring Project – Report No. 58 Executive Summary Scientific Assessment of Ozone Depletion: 2018
Explanatory Note: The Scientific Assessment of Ozone Depletion report states that HFC abundance in the atmosphere is 1.5% as a percentage of total emissions of all greenhouse gases. The Emissions Gap Report 2018 states that the annual emissions of F-Gases (HFCs, SF6 and PFCs) are 2.4%, as a percentage of the six GHGs (CO2, N2O, CH4, HFCs, SF6, and PFCs).