The world is accelerating towards a climate catastrophe, UN chief Ban Ki-moon warned on Thursday, urging rapid progress in talks to cut emissions and tackle global warming.
"Our foot is stuck on the accelerator and we are heading towards an abyss," the UN Secretary General said in a speech to the World Climate Conference.
Ban, who this week visited the Arctic to witness first hand the changes wrought by global warming, warned that many of the "more distant scenarios" predicted by scientists were "happening now."
"Scientists have been accused for years of scaremongering. But the real scaremongers are those who say we cannot afford climate action -- that it will hold back economic growth," he said.
"They are wrong. Climate change could spell widespread disaster," Ban warned.
The UN leader pinned his hopes of a breakthrough on a summit of world leaders in New York this month to discuss climate change.
Talks on extending the Kyoto protocole on emissions cuts in time for December's Copenhagen conference had been too limited and slow, he said.
"We have 15 negotiating days left until Copenhagen. We cannot afford limited progress. We need rapid progress," he added, criticising "inertia" towards climate change.
"In New York, (I) expect candid and constructive discussions. I expect serious bridge building. I expect strong outcomes," Ban told delegates and ministers from some 150 countries at the meeting in Geneva.
The United Nations chief warned that the price of failure in Copenhagen would be high "not just for future generations, but for this generation."
Ban has carried out several climate-related visits since he took the helm of the world body, including to Antarctica, to see advancing deserts in Chad and the diminishing Amazonian rainforest in Brazil.
Visibly sobered by his Arctic visit this week, he warned that rising sea levels, partly generated by melting ice in the polar region would threaten major cities and potentially up to 130 million people.
Climate change was also triggering a rush for natural resources in the Arctic as sea passages opened up, he warned.
"We are not just changing the environment, climate change is altering the geopolitical landscape," said Ban.
A report by the WWF environmental group released at the Geneva conference on Wednesday warned that the warming of polar ice, which is happening twice as fast as the global average, could affect a quarter of the world's population through flooding.
It would also have an impact on weather much further afield in the northern hemisphere, and to amplify climate change by releasing pools of greenhouse gases blamed for global warming that are currently trapped in frozen soil.