In a major step toward curbing global warming, world envoys reached an agreement Saturday to phase out potent greenhouse gases used in refrigerators and air conditioners.

Under the amendment to the 1987 Montreal Protocol on protecting the ozone layer, rich countries are to take action sooner than developing nations.

The agreement was greeted by applause from exhausted envoys who had worked through the night in the Rwandan capital Kigali to put the final touches on the deal to phase out production and consumption of hydrofluorocarbons (HFCs).

"Last year in Paris, we promised to keep the world safe from the worst effects of climate change. Today, we are following through on that promise," said UN Environment Programme chief Erik Solheim.

The US Environmental Protection Agency said, "this day will unquestionably be remembered as one of the most important in our effort to save the one planet we have".

But some representatives voiced regret that countries such as India and Gulf nations would begin the transition later than others.

"It may not be entirely what the islands wanted, but it is a good agreement," said a representative of the tiny Pacific nation of the Marshall Islands, Mattlan Zackhras.

"We all know we must go further, and we will go further".

“It was a shame that India and a handful of other countries chose a slower timeframe for phasing down HFCs," Christian Aid's senior policy advisor, Benson Ireri, said in a statement.

But he said the international community had passed its "first real test" since the Paris climate deal last year.

The Paris agreement aimed to keep global warming below two degrees Celsius (3.6 Fahrenheit), compared with pre-industrial levels. 

The elimination of HFCs could reduce global warming by 0.5 degrees by 2100, according to a 2015 study by the Institute for Governance and Sustainable Development.

Attended by representatives of nearly 200 countries including US Secretary of State John Kerry, the talks involved tough negotiations, with major developing nations like India putting up a fight over the timeline for phasing out HFCs and financing the transition.

- Could be costly -

HFCs were introduced in the 1990s to replace chemicals that had been found to erode the ozone layer, but turned out to be catastrophic for global warming.

However, swapping HFCs for alternatives such as ammonia, water or gases called hydrofluoroolefins could prove costly for developing countries with sweltering summer temperatures, such as India.

"There are issues of cost, there are issues of technology, there are issues of finances," said Ajay Narayan Jha of India's environment and climate change ministry before the deal was announced. 

"We would like to emphasise that any agreement will have to be flexible from all sides concerned. It can't be flexible from one side and not from the other."

HFCs' predecessors, chlorofluorocarbons (CFCs), were discontinued under the Montreal Protocol when scientists realised they were destroying the ozone layer.

This blanket of gas in the upper stratosphere protects Earth from the Sun's dangerous ultraviolet rays.

But it emerged that HFCs, while safe for the now-healing ozone, are thousands of times worse for trapping heat than carbon dioxide, the main greenhouse gas.

- Legally-binding agreement -

According to the Berkeley National Laboratory, air conditioning is the cause of the largest growth in HFCs -- and the world is likely to have another 700 million air conditioners by 2030. 

HFCs -- though they are greenhouse gases like carbon dioxide, methane and nitrous oxide -- are not dealt with under the Paris Agreement but under the Montreal Protocol

Under a timetable released on the website of the Montreal Protocol, rich countries will have to take action sooner than poorer nations.

Under the legally binding Kigali deal, developed countries must slash their use of HFCs by 10 percent by 2019 from 2011-2013 levels, and then by 85 percent by 2036.

A second group of developing countries, including China and African nations, are committed to launching the transition in 2024. A reduction of 10 percent compared with 2020-2022 levels should be achieved by 2029, to be extended to 80 percent by 2045.

A third group of developing countries, which include India, Pakistan, Iran, Iraq and Gulf nations, must begin the process in 2028 and reduce emissions by 10 percent by 2032 from 2024-2026 levels, and then by 85 percent by 2047.

Source: AFP