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But the outpouring of promises to tackle a problem that US President, Barack Obama, said could “define the contours of this century more dramatically than any other” was tinged by anxiety about whether the two-week meeting would strike a robust deal — the first global climate accord in 18 years.
The memory of the attacks that killed 130 people in Paris on November 13 lent a sombre tone to the opening of the talks at the Le Bourget airfield, north of the city.
In his opening address François Hollande, French president, appealed to world leaders to curb global warming, warning of famine, mass migrations and wars if they fail.
Mr Hollande told more than 20,000 attendees that climate change would bring conflict, “the risk of famine, a massive exodus from rural areas and conflicts over access to water”.
He said any deal needed to be “universal, binding and differentiated”.
Negotiators from nearly 200 countries have converged on Paris to reach an agreement to cut emissions of the greenhouse gases that scientists say are on track to warm the planet to risky levels. Any deal will be based on voluntary action plans that more than 180 nations have tabled pledges since March.
However, scientists fear that these commitments are not sufficient to prevent global temperatures warming more than 2C from pre-industrial levels, a level they deem risky for the planet. With a 1C increase nearly reached, they say evidence of a changing climate is already widespread, ranging from rising sea levels to melting ice caps.
The talks are expected to be complicated by disagreements between rich and poor nations over who should lead the fight against global warming.
Highlighting these divisions, Narendra Modi, the Indian prime minister, wrote in Monday’s Financial Times that advanced countries that “powered their way to prosperity on fossil fuel” must continue to shoulder the greatest burden. “Anything else would be morally wrong,” he says.
That point was echoed by Angela Merkel, the German chancellor, who told delegates in Le Bourget that any deal would have to be comprehensive and fair. “By comprehensive . . . we mean a profound transformation of the way we do business,” she said. “By fair, we mean that industrialised countries will have to take the lead. Emissions of the past have been caused by us.”
However, other wealthy countries say the threat of global warming cannot be addressed solely by the pool of older industrialised countries that account for a dwindling share of global emissions and that big emerging economies such as China and India must play their part.
Mr Hollande said that in order to achieve a deal that would limit the rise in global temperatures to 2C from pre-industrial times, nations would have to agree on a mechanism to review their commitments to reducing greenhouse gases every five years.
He also said that the accord must be implemented by every country and that all parts of civil society must join in.
President Obama addressed delegates, saying: “We are the first generation to feel climate change and the last that can do something about it.”
He backed Mr Hollande’s call for a “revision mechanism” so that pledges made by countries to reduce their carbon emissions could be reviewed and increased in the future. The world needed “not a stopgap solution but a long-term strategy”, he said.
Mr Hollande hinted that one of the roadblocks in the negotiations would be the $100bn in annual financing by 2020 that developed economies had committed to channel to poorer countries to help their transition to a lower carbon development model.
Mr Hollande said delegates had to agree on the rules for the 2020 goal, which was set in Copenhagen in 2009. Nations needed to define the “guarantees” on the “origins and accessibility” of the funds, Mr Hollande said.
The OECD recently reported that at least $62bn was provided in 2014, but India and other countries have questioned that figure and say the Paris accord must require wealthy countries to deliver more than $100bn a year after 2020.
Developed countries have balked at the idea of including a specific figure in the agreement, arguing that today’s governments cannot be responsible for setting budgets so far ahead.
Poorer countries might say they cannot sign up to a global deal requiring five-year review periods and other measures sought by richer nations.
Separately, billionaire philanthropist Bill Gates announced he had joined forces with a group of wealthy individuals, including the founders of Amazon and Facebook, to create a multibillion-dollar coalition to boost clean energy research and development.
Security was tight at Le Bourget, with 6,300 police officers and gendarmes deployed around the site. Several hundred special UN security forces guarded the so-called UN “blue zone” where UN offices are located.
The French authorities had banned protests in Paris as part of a state of emergency following the November 13 terror attacks.
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