Kigali (Rwanda), Oct 15: Over 150 countries struck a landmark deal on Saturday to reduce the emissions of powerful greenhouse gases, in a move that could prevent up to 0.5 degrees Celsius of global warming by the end of this century.

The amendment to the Montreal Protocol on Substances that Deplete the Ozone Layer endorsed in Kigali is the single largest contribution the world has made towards keeping the global temperature rise \"well below\" 2 degrees Celsius, a target agreed at the Paris climate conference in 2015.

\"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 chief Erik Solheim.

\"This is about much more than the ozone layer and HFCs. It is a clear statement by all world leaders that the green transformation... is irreversible and unstoppable. It shows the best investments... in clean, efficient technologies,\" Solheim said.

Commonly used in refrigeration and air-conditioning as substitutes for ozone-depleting substances, HFCs (hydrofluorocarbons) are currently the world\'s fastest growing greenhouse gases.

HFCs emissions are increasing by up to 10 per cent each year. They are also one of the most powerful gases, trapping thousands of times more heat in the earth\'s atmosphere than carbon dioxide (CO2).

\"The faster we act, the lower the financial costs will be, and the lighter the environmental burden on our children,\" said President of Rwanda Paul Kagame.

\"That begins with a clear signal that change is coming and it is coming soon. In due course, new innovations and products will allow us to phase out HFCs even faster, and at lower cost,\" Kagame said.

The rapid growth of HFCs in recent years has been driven by a growing demand for cooling, particularly in developing countries with a fast-expanding middle class and hot climates.

The amendment, named the Kigali Amendment, provides for exemptions for countries with high ambient temperatures to phase out HFCs at a slower pace.

\"It is not often you get a chance to have a 0.5 degrees Celsius reduction by taking one single step together as countries -- each doing different things perhaps at different times, but getting the job done,\" said US Secretary of State John Kerry.

\"If we continue to remember the high stakes for every country on earth, the global transition to a clean energy economy is going to accelerate,\" Kerry said.

Following seven years of negotiations, the 197 Montreal Protocol parties reached a compromise, under which developed countries will start to phase down HFCs by 2019.

As per the amendment, the A2 (developed) countries have agreed to a baseline of 2011-2013 with cuts in HFCs beginning in 2019. In fact, the US, the European Union and other countries have already started.

Whereas A5 (developing) countries have agreed to two sub-groups with two different baselines.

A5 Group 2 includes India, Pakistan, Iran and Iraq -- with a baseline of 2024 -2026 and a freeze date of 2028 (two years earlier than India had originally proposed).

China, Brazil, South Africa, Argentina and more than 100 other developing countries committed to freeze their HFC production and use by 2024.

The baseline year determines the level at which the HFC consumption in countries are capped.

By the late 2040s, all countries are expected to consume no more than 15-20 per cent of their respective baselines, says the UN Environment Programme (UNEP).

At the four-day long 28th meeting of the Parties to the 1989 Montreal Protocol on Substances that Deplete the Ozone Layer that ended Saturday, the countries also agreed to provide adequate financing for HFCs reduction, the cost of which is estimated at billions of dollars globally.

The exact amount of additional funding will be agreed at the next Meeting of the Parties in Montreal in 2017, said the UNEP.

Grants for research and development of affordable alternatives to hydrofluorocarbons will be the most immediate priority.

\"In the original proposal we have no freeze year (for HFCs) but on October 14 we clarified that we can have freeze at 2030,\" India\'s lead negotiator, Joint Secretary in the Ministry of Environment and Forests Manoj Kumar Singh told IANS.

In the second round of talks between Indian Environment Minister Anil Madhav Dave and Kerry on Friday, the freezing year was advanced to 2028 with a condition that there would be a review of technology somewhere around 2023 or 2024, Singh said.

\"If India finds that the refrigeration sector is growing at much faster rate and it cannot accommodate within the available refrigerant, then India would be free to go to 2030 as freeze year,\" he added.

Singh said the review would be done by the Technology and Economic Assessment Panel under the Montreal Protocol.

\"But it will be mutually agreed upon by India and other parties. Without India, no one can unilaterally decide what is the growth rate which will trigger that mechanism,\" he said.

For smooth transition to developing new technologies indigenously, there is a huge financial burden on India -- both for the industry and the consumers.

Alternatives to HFCs currently being explored include substances that do not deplete the ozone layer and have a smaller impact on the climate, such as ammonia or carbon dioxide.

Super-efficient, cost-effective cooling technologies are also being developed, which can help protect the climate both through reducing HFCs emissions and by using less energy.

The Kigali Amendment comes only days after two other climate action milestones: sealing the international deal to curb emissions from aviation and achieving the critical mass of ratifications for the Paris climate accord to enter into force.

Historic climate pact on greenhouse gases approved