As substitutes for ozone-depleting substances, the emissions of HFCs have increased substantially over the past two decades as a response to controls on ozone-depleting substances under the Montreal Protocol. Due to HFCs’ growing climate impact, the Kigali Amendment to the Montreal Protocol has scheduled a phase-down of their future production and consumption.

This study is designed to give policymakers quantitative feedback on the future climate benefits anticipated from the Kigali Amendment. The results 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. Additionally, this study highlights the critical need for continued high-quality, long-term records of atmospheric composition, which NOAA’s Global Monitoring Laboratory has been producing for decades.

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 Kigali-independent control 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 were 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.