The deal, which includes the world’s two biggest economies, the United States and China, divides countries into three groups with different deadlines to reduce the use of factory-made hydrofluorocarbon (HFC) gases, which can be 10,000 times more powerful than carbon dioxide as greenhouse gases. Image copyright Getty Images Image caption HFCs are commonly used in refrigerators and air conditioning systems

More than 150 countries have reached a deal described as "monumental" to phase out gases that are making global warming worse. The agreement announced Saturday morning, after all-night negotiations, caps and reduces the use of HFCs in a gradual process beginning in 2019 with action by developed countries including the United States, the world’s second worst polluter. More than 100 developing countries, including China, the world’s top carbon emitter, will start taking action by 2024, when HFC consumption levels should peak. A small group of countries including India, Pakistan and some Gulf states pushed for and secured a later start in 2028, saying their economies need more time to grow. “It’s a very historic moment, and we are all very delighted that we have come to this point where we can reach a consensus and agree to most of the issues that were on the table,” said India’s chief delegate, Ajay Narayan Jha. Environmental groups had hoped that the deal could reduce global warming by a half-degree Celsius by the end of this century. "Absolutely it's a historic day," said Durwood Zaelke, from the Institute for Government and Sustainable Development (IGSD), a long time participant in the Montreal Protocol talks. Zaelke’s group said this is the “largest temperature reduction ever achieved by a single agreement.”

The new agreement is “equal to stopping the entire world’s fossil-fuel CO2 emissions for more than two years,” David Doniger, climate and clean air program director with the Natural Resources Defense Council, said in a statement. Three-way deal

US Secretary of State John Kerry, who helped forge the deal in a series of meetings in the Rwandan capital, said it was a major victory for the Earth. International treaty designed to protect the environment against the impact of harmful substances

Created in 1987 following the discovery of a large hole in the Earth's ozone layer over Antarctica

Came into force in 1989 with the main aim of ending the use of chlorofluorocarbons (CFCs)

CFCs replaced by hydrofluorocarbons (HFCs)

Amendment proposed after scientists discovered that, while they pose no threat to the ozone layer, HFCs contribute to global warming by trapping heat radiating off the Earth

The protocol has undergone a number of revisions since it was introduced and has been successful in eliminating more than 100 fluorinated gases

Other developing countries, specifically India, Pakistan, Iran, Iraq and the Gulf states will not freeze their use until 2028.
The Obama administration agrees to an international limit on the use of hydrofluorocarbon gases in refrigeration and air conditioning.