U.S. President Barack Obama and Chinese President Xi Jinping, the heads of the world's top carbon emitters, are meeting Monday in Paris just before world leaders convene a U.N. summit in search of binding measures to address climate change.
Obama will also hold separate talks with India's Prime Minister Narendra Modi. Together, the U.S., China and India account for about half of the world's emissions of carbon dioxide, a gas that traps heat in the atmosphere and that scientists have identified as a leading cause of the rising global temperatures.
The goal of the summit is to limit average global warming to 2 degrees Celsius, perhaps less, compared to pre-Industrial Revolution levels, by curbing fossil fuel emissions that are blamed for climate change. Just this year, the U.N.'s weather agency says the average global temperature is set to rise by 1 degree Celsius, halfway to the limit the U.N. is seeking to impose.
French President Francois Hollande has warned of obstacles for the 195-nation summit in reaching a compulsory deal in Paris, including the legality of any accord, financing for poorer countries and monitoring of countries' pledges to limit greenhouse gas emissions. So far this year, 183 nations have issued long-term plans to cope with climate change, but difficult negotiations are expected at the summit and related international meetings that run through December 11.
An attempt in Copenhagen in 2009 to craft a global deal foundered at an ill-tempered summit, with divisions between rich and poor countries.
Ahead of the summit in Paris, hundreds of thousands of protesters joined worldwide demonstrations Sunday calling for adoption of global environmental controls.
Activists linked hands in the heart of the French capital amid tight security in the wake of the deadly Islamic State terrorist attacks earlier this month that killed 130 people. But peaceful protests turned violent, with police firing tear gas at some demonstrators. More than 200 protestors were detained.
With French officials banning marches, demonstrators, including U.N. Secretary General Ban Ki-Moon, left about 20,000 pairs of shoes on the ground at the Place de la Republique. Demonstration organizers said the shoes weighed four tons and included a pair the Vatican sent on behalf of Pope Francis.
Policemen clash with activists during a protest ahead of the 2015 Paris Climate Conference at the place de la Republique, in Paris, France, Nov. 29, 2015.
More than 2,000 demonstrations occurred or were set for Sunday elsewhere, including in Perth, Australia; Berlin, London, Sao Paulo and New York.
About 150 world leaders are expected at the start of the summit, including U.S. President Barack Obama, Chinese President Xi Jinping, India's Prime Minister Narendra Modi and Russian President Vladimir Putin. Even before the world leaders arrived for the official start of the summit, negotiators began talks late Sunday.
Curb global warming
The goal of the summit is to limit average global warming to two degrees Celsius, perhaps less, compared to pre-Industrial Revolution levels by curbing fossil fuel emissions that are blamed for climate change. Just this year, the U.N.'s weather agency says the average global temperature is set to rise by one degree Celsius, halfway to the limit the U.N. is seeking to impose.
As Obama got set to leave for Paris Sunday, he said U.S. leadership is "helping to drive" the effort toward cutting greenhouse gas emissions and is optimistic "about what we can achieve" at the Paris summit.
"Our businesses and workers have shown it's possible to make progress towards a low-carbon future while creating new jobs and growing the economy," Obama wrote on Facebook.
President Barack Obama (R) French President Francois Hollande (2-R), and Paris Mayor Anne Hidalgo pause for a moment of silence at the Bataclan concert hall just after midnight, Nov. 30, 2015, in Paris.
Upon arrival in Paris late Sunday, President Obama paid tribute to the victims of the recent terror attacks in the French capital. Accompanied by French President Francois Hollande and Paris Mayor Anne Hidalgo, Obama made an unannounced stop for a moment of silence at the Bataclan concert hall, site of the worst of the Paris attacks.
Three jihadist gunmen burst into the venue on November 13, shooting into the crowd and eventually blowing themselves up as police stormed the building.
Ninety people were killed at the site and many others were wounded. A total of 130 people died in the coordinated attacks in and near Paris that night.
But adoption of mandatory controls throughout the world is far from certain at the Paris summit. An attempt in Copenhagen in 2009 to craft a global deal foundered at an ill-tempered summit, with divisions between rich and poor countries.
Hundreds of pairs of shoes are displayed at the place de la Republique, in Paris, as part of a symbolic and peaceful rally called by the NGO Avaaz "Paris sets off for climate", Nov. 29, 2015.
France says that about 2,800 police and soldiers are securing the Le Bourget conference site, and 6,300 others will deploy in Paris. French Interior Minister Bernard Cazeneuve said nearly 1,000 people believed to to pose security risks have been denied entry into France.
VOA White House correspondent Aru Pande contributed to this report from Paris.