Scott Denning, Colorado State University

The U.S. Environmental Protection Agency has finalized a rule to start eliminating a class of climate-warming chemicals that are widely used as coolants in refrigerators, air conditioners and heat pumps.

If that plan feels like déjà vu, it should.

These chemicals, called hydrofluorocarbons, or HFCs, were commercialized in the 1990s as a replacement for earlier refrigerants that were based on chlorofluorocarbons, or CFCs. CFCs were destroying the ozone layer high in the Earth’s atmosphere, which is essential for protecting life from the Sun’s harmful ultraviolet radiation.

HFCs are less harmful than CFCs, but they create another problem – they have a strong heat-trapping effect that is contributing to global warming.

Several states have announced plans over the past few years for phasing out HFCs. Now the EPA, following a vote in Congress in 2020, has established federal regulations to cut HFC production and imports starting in 2022, and aims to reduce their production and use by 85% within 15 years.

If HFCs can be phased down globally – as many countries have agreed to do under the 2016 Kigali Amendment to the Montreal Protocol – that would avoid about half a degree Celsius of temperature rise compared to preindustrial times. China, a major producer of these chemicals, ratified the amendment effective Sept. 15, 2021.

Let’s take a closer look at what HFCs are and what might replace them next.

How HFCs keep rooms and food cool

Refrigerators and air conditioning use a technology known as a heat pump. It sounds almost miraculous – heat pumps use energy to take heat out of a cold place and dump it in a warm place.

Here’s how a refrigerator works: A fluid – CFCs back in the old days, and now HFCs – circulates in the walls of the refrigerator, absorbing the ambient heat to keep the fridge

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