US President Barack Obama has said the UN climate conference in Paris could be a “turning point” in global efforts to limit future temperature rises.
Negotiators from 195 countries will try to reach a deal within two weeks aimed at reducing global carbon emissions and limiting global warming to 2C (3.6F).
Leaders from 147 nations are addressing the meeting, known as COP21.
President Obama urged negotiators to deliver a meaningful deal, because the “next generation is watching”.
He told delegates: “Climate change could define the contours of this century more than any other (challenge).
“I came here personally to say the United States not only recognises the problem but is committed to do something about it.”
He added that recent years had shown that the global economy had grown while emissions had remained flat, breaking the old arguments for inaction “that economic growth and environmental protection were in conflict”.
Much of the discussions are expected to centre on an agreement to limit global warming to 2C (3.6F).
Assessments of more than 180 national climate action plans that have been submitted by countries suggest that if they were implemented the world would see a rise of nearer to 3C.
Peruvian Environment Minister Manuel Pulgar Vidal, who declared the Paris meeting open, said strong action on carbon emissions was essential for multiple reasons.
Mr Vidal, who hosted last year’s UN climate conference in Lima, said a deal would show the world that countries can work together to fight global warming as well as terrorism.
Christiana Figueres, the head of the UN’s climate change negotiations, also addressed delegates, saying never before had a responsibility so great been in the hands of so few.
“The world is looking to you,” she said. “The world is counting on you.”
UN climate conference 30 Nov – 11 Dec 2015
COP 21 – the 21st session of the Conference of the Parties – will see more than 190 nations gather in Paris to discuss a possible new global agreement on climate change, aimed at reducing greenhouse gas emissions to avoid the threat of dangerous warming due to human activities.
COP21 live: The latest updates from Paris
Explained: What is climate change?
In video: Why does the Paris conference matter?
Analysis: From BBC environment correspondent Matt McGrath
More: BBC News special report
The talks are taking place amid tight security, two weeks after attacks in Paris claimed by the so-called Islamic State (IS) group.
World leaders are attending the start of the two-week meeting to give impetus to the talks, after the high-profile failure of the Copenhagen summit in 2009.
Major points of contention include:
- Limits: The UN has endorsed a goal of limiting global warming to no more than 2C over pre-industrial levels by the end of the century. But more than 100 poorer countries and low-lying, small-island states are calling for a tougher goal of 1.5C.
- Fairness: Developing nations say industrialised countries should do more to cut emissions, having polluted for much longer. But rich countries insist that the burden must be shared to reach the 2C target.
- Money: One of the few firm decisions from the 2009 UN climate conference in Copenhagen was a pledge from rich economies to provide $100 billion (93 billion euros) a year in financial support for poor countries from 2020 to develop technology and build infrastructure to cut emissions. Where that money will come from and how it will be distributed has yet to be agreed.
Among those attending the talks is the broadcaster and naturalist Sir David Attenborough. He said he was not confident that the Paris talks would produce a deal to tackle the “hideous problem” of climate change.
“We know the consequences of a rise of temperature, what it will do for the oceans, for example,” he told the BBC.
“Increasing temperature of the oceans will cause havoc amongst the fish stocks and similarly increasing the temperature of the Earth is causing the spread of deserts.
“The problems of a rise in temperatures are huge; it has to be avoided at all costs.”
The Prince of Wales said that humanity faces no greater threat than climate change, as he issued a call for immediate action to tackle rising temperatures.
Charles told the summit: “Rarely in human history have so many people around the world placed their trust in so few.
“Your deliberations over the next two weeks will decide the fate not only of those alive today, but also of generations yet unborn.”
What is COP21?
The 21st Conference of the Parties – or COP 21 – is a meeting of 195 countries in Paris hosted by the UN, aimed at agreeing an action plan to reduce carbon emissions. It has been been billed as the last chance to limit further temperature changes.
What are the specific goals?
The ultimate aim is to limit warming to 2C (3.6F) above pre-industrial levels, widely seen as a dangerous threshold. Since 1880, the average global temperature has already risen by about 1C. About 0.6C of this has occurred in the past three decades.
Why does this matter?
When the Earth warms about 2°C above pre-industrial times, scientists say there will be dangerous and unpredictable impacts on our climate system. And we’re already half-way to that danger point.
- What is climate change?
- Why does the COP 21 conference matter?
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