U.S. Secretary of State John F. Kerry delivers a speech at the 28th Meeting of the Parties to the Montreal Protocol in Kigali, Rwanda. (Cyril Ndegeya/AFP/Getty Images)

This story has been updated.

Last week, we learned that the Paris climate agreement will go into effect in November after the European Union formally joined the accord, tipping it past the threshold needed to become a reality.

Now this week brings another major foray in international climate diplomacy, as close to 200 countries adopted an amendment to the 1987 Montreal Protocol to phase down the use of hydrofluorocarbons, or HFCs, which are super-polluting, powerful greenhouse gases.

“The prospects for the future of our planet are bright,” U.S. Environmental Protection Agency Administrator Gina McCarthy said in a statement about the deal. McCarthy led a U.S. delegation to Kigali, Rwanda, where the deal was struck early Saturday after negotiations that ran through the night.

President Obama also hailed the accord in a statement Saturday morning. “Today’s agreement caps off a critical ten days in our global efforts to combat climate change,” he said. “In addition to today’s amendment, countries last week crossed the threshold for the Paris Agreement to enter into force and reached a deal to constrain international aviation emissions. Together, these steps show that, while diplomacy is never easy, we can work together to leave our children a planet that is safer, more prosperous, more secure, and more free than the one that was left for us.”

HFCs don’t get much attention. But here’s why they matter: When the original Montreal Protocol phased out chlorofluorocarbons, which were destroying the planet’s ozone layer, manufacturers had to find a replacement chemical to use as refrigerants and in other industrial applications.

Along came HFCs, which were much better for the ozone layer but, like CFCs, also happen to be a strong global warming agent. The chemicals are vastly more powerful than carbon dioxide over a 100 year time frame when it comes to warming the atmosphere. So one huge environmental crisis was, in effect, replaced by another problem lingering on the horizon.

Scientists fear that a forecast explosion in air conditioning all around the world, especially in developing economies like India, could result in so much HFC leakage that it could warm the global temperature by an additional half a degree Celsius by the end of the century, which would blow past warming thresholds outlined in the Paris agreement. Unless, that is, HFCs are curbed.

Under the “Kigali Amendment” approved early Saturday, the planned reduction of HFCs would have an impact similar to the removal of 80 billion tons of carbon dioxide from the atmosphere over the next 35 years, according to the Natural Resources Defense Council.

U.S. Secretary of State John F. Kerry, who was also on hand for the negotiations said in a speech Friday that “it is not often you get a chance to have a .5-degree centigrade reduction by taking one single step together as countries — each doing different things perhaps at different times, but getting the job done.”

Paul Bledsoe, who worked on climate issues under President Bill Clinton in the 1990s and was in Kigali for the negotiations, said the agreement could help “lessen climate change impacts like sea-level rise, wildfires, and extreme storms and floods.” In addition, “it should jump-start other efforts to get to prevent runaway climate change,” he said.

The way the new amendment works is this: Developed and developing countries will have different “freeze dates,” or years when they must peak their HFC emissions and then begin to bring them down steadily over time. And in many cases, those freeze dates will be quite soon. For developed nations like the United States, the date will be 2019. For the majority of developing nations, it will be 2024, except for a few nations, including India and Pakistan, which will take a little longer, until 2028.

Some observers said that last development is a bit of a speed bump — but not a very serious one. “We came to take a half a degree Celsius out of future warming, and we won about 90 percent of our climate prize,” said Durwood Zaelke, the head of the Institute for Governance & Sustainable Development.

But this HFC phase-down won’t just happen by international fiat. Zaelke said economic forces will now kick in to push manufacturers away from using HFCs and toward drawing on different chemicals. And that could make up the difference.

“Every time we’ve done a past phase out, [the Protocol] has exceeded the dates, because the market moves faster,” said Zaelke, who also spoke from Kigali. “The market knows how to read these signals very well and the smart money has been moving [to] the climate friendly substitutes. That’s been underway, and this is the accelerant, and also the lock-in.”

One major industry group, the U.S.-based Air-Conditioning, Heating, and Refrigeration Institute, hailed the agreement Friday, and signaled that the quest for alternatives is on. “The agreement is just the first step in a multistep process,” said the group’s president, Stephen Yurek, in a statement. “Our industry is hard at work doing the research on the HFC alternatives that will be used in the world’s air conditioners, heat pumps, and refrigeration equipment, and getting that right is certainly as important as reaching agreement.”

The upshot is that on November 7, when nations of the world gather in Marrakesh, Morocco, for a key United Nations climate meeting, they will not only have the Paris agreement in force far earlier than anyone initially expected, but will also be operating with a new HFC regime. All of which marks 2016 as quite the year for international climate progress.

Read more at Energy & Environment:

Greenland’s ice is melting from both above and below — and scientists say they’re connected

Al Gore and Hillary Clinton just strongly linked Hurricane Matthew to climate change

How the Earth will pay us back for our carbon emissions with … more carbon emissions

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