On Saturday, nearly 200 countries signed a deal to limit the use of some powerful greenhouse gases in a major new effort to fight climate change.
Meeting in the Rwandan capital of Kigali, negotiators stayed up all night to reach a final deal amending the Montreal Protocol to make serious cuts to the use of hydrofluorocarbons, or HFCs.
The factory-made chemicals represent only a small fraction of total emissions, but can be thousands of times more potent than carbon dioxide.
What are HFCs?
Hydrofluorocarbons are a type of greenhouse gas made up of an unnatural group of compounds containing carbon, fluorine, and hydrogen.
HFCs are created through human-related activities, including industry and manufacturing, according to the EPA.
HFCs can live in the atmosphere for a very, very long time and are only removed when they are destroyed by sunlight in the far upper atmosphere.
"HFCs are among the most potent and longest lasting type of greenhouse gases emitted by human activities," the EPA advises.
Where are HFCs found?
HFCs are used as refrigerants, aerosol propellants, solvents, and fire retardants.
Your fridge, the air conditioner in your house, and the one in your car may all be guilty of pumping HFCs into the atmosphere.
HFCs can leak out during the manufacturing process if your air conditioner or refrigerator has a leak, or if the units are disposed of improperly.
Once in the atmosphere, HFCs can trap thousands of times as much heat as carbon dioxide, contributing to global warming and climate change.
What is the Montreal Protocol?
The Montreal Protocol is an international treaty created in 1987 to protect the ozone layer by phasing out the production of numerous substances that were responsible for ozone depletion.
As a result of the international agreement, the ozone hole above Antarctica has been slowly recovering and climate projections indicate the ozone layer will return to 1980 levels between 2050 and 2070.
In recent years, campaigners have shifted their focus to amending the protocol to phase out HFCs.
Because the treaty is already in force, the amendment reached Saturday is legally binding on member nations.
What are the specifics of the new agreement?
The goal of the agreement is to phase out the use of HFCs worldwide — but that will take some time.
In the meantime, the main points of the agreement are:
* The world's richest countries, including the United States and those in the European Union, will freeze the production and consumption of HFCs by 2018, reducing them to about 15% of 2012 levels by 2036.
* The bulk of the rest of the world, including China, Brazil, and all of Africa, will freeze HFC use by 2024, reducing it to 20% of 2021 levels by 2045.
* And a small group of the world’s hottest countries — India, Pakistan, Iran, Saudi Arabia, and Kuwait — will be required to freeze HFCs use by 2028 and reduce it to about 15% of 2025 levels by 2047.
It's hoped this agreement will stop the equivalent of more than 80 billion metric tons of carbon dioxide being released into the atmosphere by 2050 and help avoid warming of up to 0.5°C by the end of the century.
What has been the reaction to the deal?
US President Barack Obama hailed the agreement, calling it an "ambitious and far-reaching solution" to what he described as a "rapidly growing threat to the health of our planet", saying:
Today's agreement caps off a critical 10 days in our global efforts to combat climate change. 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.
Secretary of State John Kerry, who was in Kigali for the deal, also praised the deal. "The world came together today in yet another milestone on the path toward a safer, more sustainable future," he said in a statement.
“It is likely the single most important step we could take at this moment to limit the warming of our planet and limit the warming for generations to come," he told reporters. “It is the biggest thing we can do in one giant swoop.”
Al Gore, the former vice president and climate campaigner, also described it as "an encouraging step forward."
"This is about much more than the ozone layer and HFCs," said Erik Solheim, executive director of the UN Environment Program, in a statement. "It is a clear statement by all world leaders that the green transformation started in Paris is irreversible and unstoppable,"
“It’s not the best deal we could have got, but it’s a good deal,” Mattlan Zackhras, a negotiator from the Marshall Islands, a low-lying Pacific nation threatened by rising sea levels, told the Associated Press. “We all know we must go further, and we will go further."
Will I have to say goodbye to air-conditioning eventually?
No, the phase-out will be gradual and several companies are already working on cooling replacements for HFCs, the New York Times reports.
Alicia Melville-Smith is a homepage editor and reporter for BuzzFeed News and is based in London.
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