evident in extreme weather - economic slowdown and arguments over who should pay have all but killed any chance of a meaningful extension to the expiring Kyoto Protocol.
Almost 200 nations meet in Doha, Qatar, from November 26 to December 7 to at least try. But Russia, Japan and Canada, major economies that signed the Kyoto Protocol in 1997, have already said they will not sign up to emissions cuts beyond December 31.
The huge developing economies of India and China, now the world's biggest emitter of gases such as carbon dioxide from fossil fuels that trap the sun's heat, were anyway not obliged to cut emissions under the Kyoto process.
But campaigners say failure to extend Kyoto will also hobble Doha's much harder challenge: to work on an entirely new treaty to cap emissions from all countries including developing nations, due to be agreed by 2015 and go into force in 2020.
Meanwhile, man-made climate change is ever more visible.
Arctic sea ice thawed in September to its lowest recorded level, and extreme heat waves and drought have hit the United States and Russia more often than would be expected from historical records, a World Bank report said last week.
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Greenhouse gas levels hit a new record last year, despite a world economic slowdown.
Even if all countries fulfil existing commitments, the world will warm by more than 3 degrees Celsius (5.4 Fahrenheit) by 2100 - more than the 2 degrees that the countries of the world say should be the limit, and dwarfing the 0.8 degree rise seen since 1900.
Heatwaves and floods
Rising sea levels and more floods, heatwaves, storms and droughts will be the result, the scientists of the UN climate panel say. Less predictable rainfall and higher temperatures are likely to disrupt food and water supplies for a rising population.
Know more about Kyoto protocol
The probability that the change is man-made is now at least 90 percent, the panel says.
"It's abundantly clear every day that what's been committed to is far from what's needed, and you can't wait until 2020 to be increasing the level of ambition," said Jennifer Morgan of the World Resources Institute in Washington.
But Russia, Canada and Japan have said they will not make cuts under a Kyoto Two because they would be meaningless when emerging nations led by China and India have no targets.
Kyoto bound almost 40 developed nations to cut emissions by an average of at least 5.2 percent from 1990 levels by 2008-12, but also established carbon trading mechanisms, which Russia, Canada and Japan want to preserve.
A cloud of smoke goes out from a chimney in a winter sky in Seclin, northern France. AFP photo/File
The United States never ratified the Kyoto deal, arguing that it would cost US jobs and that it should include emissions cuts for poorer nations.
If it is allowed to expire, the world will have no legally binding climate plan from 2013, merely national emissions cuts by countries including the European Union, Australia and Ukraine that account for just 12 to 14 percent of global emissions.
The EU has promised a cut in emissions of at least 20 percent below 1990 levels by 2020, with or without Kyoto, to drive its carbon market. It argues that cutting emissions makes sense to gain a lead in developing greener technologies.
But many fear that much of the remaining momentum for a shift away from fossil fuels to greener energies such as wind and solar power may be lost, especially as the fight for any kind of economic growth has pushed green issues off the agenda.
Helen Clark, head of the UN Development Programme, said work to stem rising temperatures had been "painfully slow" but that a failure to extend Kyoto would be "extremely serious" for the fight against climate change.
Factbox: Climate negotiating positions of big greenhouse emitters
China, India, Brazil and South Africa this week urged an extension of Kyoto as "the essential basis for ambition", with deeper cuts by rich nations.
Trash clogs up a polluted canal at the edge of Beijing. China said that two-thirds of its cities currently fail to meet new air-quality standards introduced this week that are based on the pollutants most harmful to health. AFP photo/File
They said a new deal from 2015 should preserve a split between rich and poor nations, enshrined in the 1992 climate convention, that obliges developed nations to lead since they have benefited most from burning fossil fuels.
The United States and other rich countries say the 1992 division is outdated. China is now the world's largest emitter of carbon dioxide and has overtaken Russia as the number two cumulative emitter in history behind the United States.
Lack of progress in recent years, including the failure of the Copenhagen summit in 2009, is partly tied to China's desire to burn more energy to boost growth and US President Barack Obama's inability to persuade the Senate to cut US emissions.
Obama said last week that he was a "firm believer" that climate change was real and that there was an "obligation to future generations to do something about it" even as he reaffirmed that his second-term priority would be the economy.
This photo clicked in 2001 shows the massive B-15A iceberg that stretched for 150 kms across McMurdo Sound after it broke off the Ross Ice Shelf in Antartica. AFP Photo
"China wants a few years to grow before it caps its emissions. And the US is happy with that," said Heike Schroeder of the University of East Anglia in England, who believes that a radical overhaul is needed to revitalise the UN talks.
Developing nations also want assurances in Doha of more aid after the end of a three-year, $10 billion-a-year "fast start" programme intended to promote their use of non-fossil fuels, especially since the rich countries have set a long-term goal of $100 billion a year from 2020.
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