An area of Arctic sea ice bigger than the United States melted this year, according to the UN weather agency, which said the dramatic decline illustrates that climate change is happening "before our eyes".
In a report released at UN climate talks in the Qatari capital of Doha, the World Meteorological Organization said the Arctic ice melt was one of a myriad of extreme and record-breaking weather events to hit the planet in 2012.
Droughts devastated nearly two-thirds of the United States as well western Russia and southern Europe.
Floods swamped west Africa and heat waves left much of the northern hemisphere sweltering.
But it was the ice melt that seemed to dominate the annual climate report, with the UN concluding ice cover had reached "a new record low" in the area around the North Pole and that the loss from March to September was a staggering 11.83 million square kilometres — an area bigger than the United States.
"The alarming rate of its melt this year highlighted the far-reaching changes taking place on Earth's oceans and biosphere," WMO Secretary-General Michel Jarraud said.
"Climate change is taking place before our eyes and will continue to do so as a result of the concentrations of greenhouse gases in the atmosphere, which have risen constantly and again reached new records."
The dire climate news — following on the heels of a report that found melting permafrost could significantly amplify global warming — comes as delegates from nearly 200 countries struggled for a third day to lay the groundwork for a deal that would cut emissions in an attempt to ensure that temperatures don't rise more than 2C over what they were in preindustrial times.
Temperatures have already risen about 0.8C, according to the latest report by the IPCC.
Discord between rich and poor countries on who should do what has kept the two-decade-old UN talks from delivering on that goal, and global emissions are still going up.
Rajendra Pachauri, chairman of the Intergovernmental Panel on Climate Change, which shared the Nobel Peace Prize in 2007 with former US Vice President Al Gore, urged delegates to heed the science and quickly take action.
"When I had the privilege in 2007 of accepting the Nobel Peace Prize on behalf of the IPCC, in my speech I asked the rhetorical question, 'Will those responsible for decisions in the field of climate change at the global level listen to the voice of science and knowledge, which is now loud and clear,'" he said.
"I am not sure our voice is louder today, but it is certainly clearer on the basis of the new knowledge."
Delegates in Doha are bickering over money from rich countries to help poorer ones adapt to and combat the impacts of climate change, and whether developed countries will sign onto an extension of a legally binding emissions pact, the Kyoto Protocol, that would run until 2020.
A pact that once incorporated all industrialised countries except the United States would now include only the European Union, Australia and several smaller countries which together account for less than 15 per cent of global emissions. And the United States is refusing to offer any bolder commitments to cut its emissions beyond a non-binding pledge to reduce emissions by 17 per cent below 2005 levels by 2020.
"For developed country parties like the United States and the European Union, the pledges and commitments... put forward on the table are far below what is required by the science," Su Wei, a member of the Chinese delegation, told reporters.
"And far below what is required by their historical responsibility."
Developing countries have said they are willing to take steps to control emissions, but that they must be given space to build their economies.
Although China is the largest carbon polluter and India is rapidly catching up, both countries lag far behind the industrial countries in emissions per person and still have huge populations mired in poverty. They don't see emissions peaking anytime soon.
"We are still in the process of industrialisation. We are also confronted with the enormous task of poverty eradication," said Wei, acknowledging that the country's emissions won't peak by 2020.
"In order to eradicate poverty, to try to improve the living standards, certainly we need to develop our economy," he said.
"So the emissions will need to grow for a period of time."
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