Northern China choked under some of the worst smog this year on Monday, with Beijing's pollution soaring to 22 times healthy limits, triggering the city's second-highest air alert on the eve of global climate change talks.

Thick haze blanketed cities across the country after President Xi Jinping arrived in Paris for the talks where China, the world's largest emitter of greenhouse gases, will be central to discussions.

World leaders opened an historic summit in the French capital on Monday with "the hope of all of humanity" laid on their shoulders as they sought a deal to avert a climate catastrophe.

The heads of more than 150 nations kicked off 12 days of talks in search of an elusive pact that would indirectly restructure the world economy, weaning it off fossil fuels that stoke global warming.

Climate negotiators in Paris vowed Sunday to craft an historic pact to avert catastrophic global warming in honor of the victims of this month's horror attacks in the French capital.

The undertaking was made as negotiators met ahead of Monday's formal opening of a two-week conference tasked with forging a pact unifying long-bickering nations in the struggle to end the world's dependence on climate-altering fossil fuels.

Protesters linked hands near the violent heart of the Paris terror attacks Sunday, giving an emotional jolt to world leaders flying into the French capital to try to save Earth from a climate catastrophe.

As hundreds of thousands of people joined worldwide protests, the human chain aimed to send a highly symbolic message to leaders on the eve of the official opening of a 195-nation UN climate summit in Paris.

The campaign to sell off investments in fossil fuel projects, particularly those involving coal, is no longer a fringe movement as big players like banks and investment funds get on board.

The divestment campaign has come a long way from its beginnings in the United States, where students began pressuring their university investment funds in 2008 to pull their money out of companies connected with fossil fuels.

Thousands turned out for climate change marches in Manila and Brisbane Saturday, part of a weekend of action across the globe to demand results from next week's historic Paris summit.

Religious clergy, students and activists marched through the Philippine capital calling for curbs on emissions to mute the impact of climate change, which is blamed for a spike in typhoons and extreme weather that has wreaked havoc on the nation.

Broke, remote and deprived of jobs -- just 25 years ago, the border town of Guessing close to Hungary was one of the poorest in Austria, a forgotten frontier along the Iron Curtain trail.

Yet today, the municipality of 4,000 people has morphed into a global flagship model for green energy, after becoming the first community in the European Union to produce all its heat and power from renewable sources back in 2001.

Medical experts say climate change affects human health in direct ways, by the spread of water- and mosquito-borne diseases for example, and indirectly, such as through hunger.

Here is a snapshot of the problem:

Latin America will demand that the richest and most polluting countries foot the bill for reducing harmful emissions at the world climate summit starting Monday.

Countries in one of the world's poorest and most environmentally diverse regions have failed to agree on many things and do not have a common negotiating position overall going into the talks.

Over the past 15 years – and contrary to popular belief – the world has made tremendous progress in reducing global poverty. One billion fewer people live in extreme poverty today than in 2000. This year, the rate of extreme global poverty is expected to fall below 10%, dropping into single digits for the first time in history. Inclusive economic growth, especially in China and India, has driven this success.

This kind of economic growth, which increases the income of the poorest 40%, is critical to reaching our global goal of ending poverty by 2030.