U.N. Secretary-General Ban Ki-moon told world leaders gathered Monday in Paris that their major climate summit "must mark a decisive turning point" and that they "have the power to secure the wellbeing of this and succeeding generations."
"You are here today to write the script for a new future, a future of hope and promise of increased prosperity, security and dignity for all," Ban said. "We need the world to know that we are headed to a low-emissions, climate resilient future and there is no going back."
More than 150 leaders are taking part in the summit as they try to agree on binding measures to curb fossil fuel emissions and limit the global temperature from warming to 2 degrees above pre-Industrial Revolution levels. The U.N. 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 in order to prevent potentially catastrophic global effects.
Obama, Xi meeting
Before the summit opened, U.S. President Barack Obama met with Chinese President Xi Jinping and said the two countries have a common vision of what is needed in an agreement, including steps toward a low carbon global economy and helping financial support to help developing nations adapt.
"As the two largest economies in the world and the two largest carbon emitters, we have both determined that it is our responsibility to take action, and since our historic joint announcement of our post-2020 climate targets in Beijing last year, more than 180 countries have followed in announcing their own targets," Obama said. "So our leadership on this issue has been absolutely vital."
The U.S. has pledged to cut emissions up to 28 percent by 2025, while China said targets to peak its emissions by about 2030.
Obama will also hold separate talks Monday 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.
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 Paris summit, 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. 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.
France says 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 pose security risks have been denied entry into France.