Global warming from refrigerant HFCs is underestimated by their CO2 equivalent emissions within the century

Abstract HFC refrigerant gases are the fastest growing atmospheric GHGs and amongst the most potent. Yet, unlike methane (a short-lived GHG akin to most refrigerants but with significantly lower GWPs), the errors in estimating refrigerant warming based on CO2-equivalent metrics are unknown. We model scenarios to show how the atmospheric responses (i.e., concentrations, forcing and warming) of HFC emissions compare to their CO2-equivalents. Analyzing the remaining warming from HFC emissions if the Kigali Amendment to the Montreal Protocol is achieved, we report that CO2-equivalents omit a warming peak in 2046. A standardized emission step-change shows that calculating warming from CO2-equivalents underestimates the benefits of reducing short-lived HFC emissions by a factor of 4-17 in 2030 (and by 3-5 in 2050). We also demonstrate how natural removals of individual short-lived HFCs are unaccounted when estimating warming from CO2-equivalents. To avoid misrepresentation of global warming from refrigerants, careful consideration of metrics is needed.