London/Washington: A landmark global accord to combat climate change officially took effect on Friday, putting pressure on countries to take action to slash greenhouse gas emissions and limit global warming.
The 2015 Paris Agreement won swift backing last December by almost 200 countries including China, the United States and the European Union and has been described as the most complex global treaty since the Marrakesh (trade) Agreement, signed in 1994.
The accord passed a threshold on October 5 of 55 nations accounting for more than 55 per cent of greenhouse gas emissions, allowing it to come into force 30 days later.
A previously anticipated timeframe was given as 2020 but ratification was swift compared to other international treaties, showing strong international support. However, around 100 countries have yet to agree and much work needs to be done on the fine detail of the pact to ensure it is not watered down.
"This is a moment to celebrate. It is also a moment to look ahead with sober assessment and renewed will over the task ahead," United Nations' climate chief Patricia Espinosa said in a statement.
"In a short time - and certainly in the next 15 years - we need to see unprecedented reductions in greenhouse gas emissions and unequalled efforts to build societies that can resist rising climate impacts," she said.
The Paris Agreement seeks to wean the world economy off fossil fuels in the second half of the century, limiting the rise in average world temperatures to "well below" 2.0 degrees Celsius (3.6 Fahrenheit) above pre-industrial times.
It also notes an ambition to limiting temperature rise even further to 1.5 degrees.
The pact kicked off a rolling start in the Pacific region on Thursday, home to low-lying islands states which are in danger of rising sea levels.
On the same day, the annual report of UN Environment analysed countries' current pledges for emission cuts and said they were not sufficient.
Even if emission-cutting pledges under the Paris agreement are fully implemented, predicted 2030 emissions could put the world on track for a temperature rise of 2.9 to 3.4 degrees Celsius this century, the report said.
The latest round of UN climate talks begin on Monday in Marrakesh, Morocco, where representatives from countries will try to find ways to implement the agreement.
The US presidential election could also be a main focus of the talks in the first week if Republican candidate Donald Trump wins, as he has threatened to reject the accord.
Environmental campaign groups, as well as some businesses, investors and academics said the meeting in Marrakesh must keep up the spirit of international support for climate action.
"As the world heads into (the meeting) in Marrakesh, we must regain the sense of urgency we felt a year ago," World Bank Group President Jim Yong Kim said.
A global policy framework which favours low-carbon energy generation will also challenge traditional business models for power utilities and oil, gas and coal producers.
"Hydrocarbon fuel consumption is in the firing line and energy sector impacts are being felt already, despite Paris Agreement targets not kicking in until the end of the decade," said Paul McConnell, research director for Global Trends at consultancy Wood Mackenzie.