The head of the United Nations climate panel has painted a stark picture of the future unless nations agree tough emissions curbs to control global warming.
Rajendra Pachauri was speaking at the opening of the United Nations climate change conference in Copenhagen on Monday.
Dr Pachauri told delegates from 192 countries that without steps to curb the rapid growth of carbon emissions and deforestation, climate change is likely to threaten the livelihoods of billions of people.
Campaigners say politicians have two weeks to save the Earth from catastrophic climate change in the talks, which end on 18 December with a summit of 105 world leaders, including United States President Barack Obama.
Danish Prime Minister Lars Loekke Rasmussen described the summit as an opportunity the world cannot afford to miss and a chance for leaders to safeguard humanity.
Any agreement made at Copenhagen is intended to supplant the 1997 Kyoto Protocol on climate change, the first phase of which expires in 2012.
The New Zealand delegation is being led by Nick Smith, the Minister for Climate Change Issues. Prime Minister John Key is to attend the leaders' summit.
Mr Key says the political momentum building around the conference is positive and believes a high-level political agreement could be reached - with further work next year producing a binding deal.
Meanwhile, deep divisions have already emerged at the talks.
The ABC reports a representative of the developing world says the amount of money set aside to help poor nations adapt to climate change - $US10 billion - is an insult.
Sudan holds the presidency of the group of 77 developing nations, and its negotiator attacked the European Union and the United States for what he called insufficient emissions cuts.
Rich nations have been told they should commit $US40 billion a year in new money to help Africa tackle the consequences of global warming.
African Development Bank president Donald Kaberuka said he wanted to see a "willingness by rich countries to dig into their pockets to enable low-income countries to adapt to climate change."
Saudi Arabia's chief negotiator has raised issues about the validity of the scientific research used to justify claims that global warming is man-made.