This past weekend, a sequel to the Paris climate agreement has taken shape in Vienna, Coral Davenport reports for The New York Times. Despite little fanfare, Davenport reports, many environmentalists are calling this the “most significant action this year to reduce global warming.”

While the Paris Agreement aims to reduce emissions from greenhouse gases like coal and oil, negotiators in Vienna are moving ahead on a deal to ban hydrofluorocarbons, or HFCs, commonly used in refrigerators and air conditioners. Despite only contributing a small amount to the world’s total greenhouse gas emissions, HFCs can trap heat in the atmosphere at rates a thousand times higher than carbon dioxide, published studies have shown.

The draft language coming out of Vienna is the work of seven years of negotiations, Davenport explains. But this draft could lead to a deal ready to be signed at the 28th Meeting of the Parties to the Montreal Protocol in Rwanda in October.

This deal would be an amendment to the Montreal Protocol, the 1989 environmental treaty that aimed to protect the ozone layer by banning ozone-depleting chlorofluorocarbons, or CFCs. Chemical companies created HFCs to replace CFCs, and while HFCs do not deplete the ozone, they do have unexpected and powerful heat-trapping abilities, worsening climate change.

Studies show that worldwide banning of HFCs alone could prevent nearly one degree of global warming over the next century. In a speech to negotiators in Vienna on Friday, Secretary of State John Kerry stated that “Amending the Montreal Protocol to phase down HFCs is one of the single most important unitary steps that we could possibly take at this moment to stave off the worst impacts of climate change and to protect the future for people in every single corner of the globe.”