More than 150 countries have reached a landmark deal in Kigali, Rwanda to reduce emissions of a powerful chemical used in refrigeration and air conditioning.
The U.N. calls this a "breakthrough" against climate change because the pact signed Saturday could prevent global temperatures from rising "up to 0.5 degrees Celsius by the end of this century" – though some experts say the impact may fall short of 0.5 degrees.
This deal tackles hydrofluorocarbons (HFC), which are commonly used in refrigerators and air conditioners. This type of greenhouse gas is extremely powerful – it can trap "thousands of times more heat in the Earth's atmosphere than carbon dioxide," according to the United Nations Environment Programme.
The U.N. says Saturday's agreement is a major step toward the goal of "keeping the global temperature rise 'well below' 2 degrees Celsius, a target agreed at the Paris climate conference last year."
The major climate accord reached in Paris last December offers voluntary pledges, as The New York Times reported, which are "often vague and dependent on the political will of future leaders." This new deal offers "offers specific timetables to replace HFCs with more planet-friendly alternatives," and "maintains the legal force of a treaty," according to the Times.
In comparison to the Paris accord, the outcome of the Kigali agreement "could have an equal or even greater impact on efforts to slow down the heating of the planet," as the Times reported.
"This is about much more than the ozone layer and HFCs. It is a clear statement by all world leaders that the green transformation started in Paris is irreversible and unstoppable," U.N. Environment chief Erik Solheim said in a statement. "It shows the best investments are those in clean, efficient technologies."
The agreement, which is billed as a compromise, sets out a schedule for countries to phase down their HFC consumption.
"Developed countries will start to phase down HFCs by 2019," UNEP said. That includes the U.S. and the European Union. "Developing countries will follow with a freeze of HFCs consumption levels in 2024, with some countries freezing consumption in 2028."
The countries starting to reduce their emissions in 2028 include India, Pakistan, and some Gulf states, as The Associated Press reported. They had lobbied for a later start, "saying their economies need more time to grow."
According to the BBC, China, "the world's largest producer of HFCs, will not actually start to cut their production or use until 2029."
The delayed start given to major emissions producers like China and India is causing some environmental advocates to question whether the agreement can actually fulfill its promise of preventing global temperatures from rising 0.5 degrees.
"They needed an agreement here as it's seen as an Obama legacy, so the US delegation has been pretty aggressive in making China and India get to an agreement," Paula Tejon Carbajal from Greenpeace International tells the BBC. "It's an incremental step towards 0.5 degrees but its not there yet, they say that the market will work to get us there, but we are not there yet."
Still, this is the "largest temperature reduction ever achieved by a single agreement," as the Institute for Governance & Sustainable Development termed it. The group's president, Durwood Zaelke, said this agreement amounted to about 90 percent of what they were hoping for – and he's optimistic that market transformation will take care of the rest.
U.S. Secretary of State John Kerry said this was "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," as the Times reported. He added that it is "the biggest thing we can do in one giant swoop."
The pact is an amendment to 1987's Montreal Protocol, which the U.N. credits for "a 98 percent decrease in the production and use of ozone-damaging chemicals."