But the extent of COVID-19 mitigation will tell the tale. Over the past 15 years, natural refrigerants – particularly CO 2 (R744) and propane (R290), as well as ammonia (R717) – have become recognized as the most environmentally friendly and future-proof replacement for HCFCs and HFCs in commercial and industrial refrigeration. The change began in Europe, prompted by the advent of the EU F-Gas Regulation in 2006, and caught on in Japan, where CO 2 had already made its mark in heat pump water heaters. Other regions like the U.S., Australia/New Zealand and South Africa have come later to the party. In 2021, two world-historical events should help drive uptake in installations of natural refrigerant-based systems throughout the world. First is the growing urgency of the climate crisis, as the prevalence of wildfires, droughts, extreme storms, rising sea levels and other damaging effects becomes inescapable. The other is the replacement of climate denialist Donald Trump as president of the U.S. by Joe Biden, who has promised an ambitious program to tackle climate, including many refrigerant-related initiatives.