A final deal to phase out hydrofluorocarbons—chemicals commonly used in heating, air-conditioning and refrigeration systems—has drawn a step nearer as negotiators from nearly 200 countries meeting in Vienna made progress on ending the use of HFCs, which are seen as a major cause of global warming.

U.S. Secretary of State John Kerry told officials at the July 22 meeting that gradually bringing the use of HFCs to a halt “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.”

Environmental groups say HFCs have been shown to contribute more than carbon dioxide emissions to the earth's rapid warming: They also trap heat in the  atmosphere. “Pound for pound, the climate impact of HFCs is thousands of times greater than that of carbon dioxide,” David Doniger, director of the Natural Resources Defense Council’s climate and clean-air program, said in a blog post.

The July 22-23 meetings in Vienna continued talks held last year to amend the Montreal Protocol and phase out HFCs over five to 15 years. The Montreal Protocol treaty, signed in 1989, aimed to protect the ozone layer by eliminating the use of chlorofluorocarbons (CFCs) and replacing them with HFCs.

HFCs do not deplete ozone but trap more heat in the Earth’s atmosphere. The Obama administration, along with environmental groups and the heating-and-refrigeration industry, have advocated modifying the Montreal Protocol to require more climate-friendly alternatives for HVAC units to be developed and installed.

Kerry said the Montreal Protocol was enormously successful. The worst CFCs have been phased out since the treaty was signed, and, “as a result, the hole in the ozone is shrinking and on its way to repair,” he added.

The key sticking points during the Vienna talks were the schedule for winding down HFC use and how much financial assistance developed countries will provide to developing nations.

Representatives of developing countries, whose HFC use is projected to grow significantly over the next several decades, say they would disproportionately suffer the consequences of a shorter phase-out period.

They advocate a 15-year timetable; the U.S. has called for a phase-out in five years as well as financial help for meeting that more-aggressive schedule.

Officials will meet in Rwanda in October, aiming to produce a final agreement.

Frank Maisano, a partner with Bracewell and Guiliani’s policy-resolution group, said in a recent issue of his online newsletter that the talks were “a huge success that likely will dwarf the uncertainty of cuts that the Paris Treaty [on climate change] may or may not produce.”

Maisano noted that the HVAC industry has been pushing for years for an amendment to phase out HFCs. “A global agreement creates predictability for producers and manufacturers alike and eliminates the hodgepodge of different HFC-reduction schemes that they would surely face as the world’s focus on climate change continues,” he said.