The 12-day United Nations talks opened amid a slew of warnings about potentially disastrous warming with increasingly extreme weather phenomena unless humankind changes its atmosphere-polluting, fossil-fuel burning ways.
"What happens in this stadium is not a game. There are not two sides but the whole of humanity. There are no winners and losers, we all either win or lose in the future we make for ourselves," UN climate chief Christiana Figueres told climate negotiators.
"The second is the devastating impact of Typhoon Haiyan, one of the most powerful typhoons to ever make landfall. Our thoughts and our prayers are with the people of the Philippines, Vietnam and South-East Asia."
The UN has set a target of limiting global average warming to two degrees Celsius over pre-Industrial Revolution levels -- at which scientists believe we can avoid the worst effects of climate change.
Reducing this pollution requires a costly shift to cleaner, more efficient energy, which helps to explain why the UN negotiations have been such a battlefield.
Experts say the 2 C objective, set in 2009, is likely to be badly overshot on current emissions trends.