Ban Ki-moon, the United Nations Secretary-General, has warned of "catastrophic consequences" unless a new international agreement on greenhouse gas emissions is reached.
By Jon Swaine Published: 1:12PM BST 10 Aug 2009
Climate change is "simply the greatest collective challenge we face as a human family", Mr Ban said in a speech on Monday in Seoul.
He urged international leaders to reach a deal to limit their countries' carbon emissions at the UN climate conference in Copenhagen in December.
A replacement for the 1997 Kyoto protocol, which expires in 2012, is supposed to be negotiated at the summit. Mr Ban said the leaders had a "once-in-a-generation opportunity".
"We have a chance to put in place a climate change agreement that all nations can embrace, which will be equitable, balanced, comprehensible," Mr Ban said.
"The world has less than 10 years to halt the global rise in greenhouse gas emissions if we are to avoid catastrophic consequences for people and the planet."
He called on governments to "seal the deal in the name of humankind" through a "renewed multilateralism, a compassionate multilateralism."
Mr Ban said that the threat of climate change was made worse because of other era-defining crises. "We are living through an age of multiple crisis," he said. "Fuel, flu and food, and most seriously, financial. Each is something not seen for years, even for generations. But now they are hitting us all at once."
World leaders are likely to arrive in Copenhagen with sharply different views on the amount by which carbon emissions should be reduced.
The countries of the European Union have already committed themselves to a 20 per cent cut on 1990 emissions levels by 2020, followed by an 80 per cent cut by 2050.
New Zealand announced on Monday that it would cut emissions by 10 to 20 per cent below 1990 levels by 2020.
However, the US Senate is expected to pass a bill to cut emissions by only 17 per cent on 2005 levels by 2020.
Meanwhile China and India, both keen to protect their ability to continue mass industrialisation, have refused to offer any specific targets for cuts to their emissions. They are also insisting that both Europe and the US commit to 40 per cent cuts in emissions by 2020 against 1990 levels.
The Pacific Islands Forum, representing the group of low-lying island nations threatened by rising sea levels, last week urged cuts of 45 per cent.
Scientists have warned that reductions of 25 to 40 per cent are needed to prevent global temperatures from rising 2 degrees C (3.6 degrees F).
Last week Yu Qingtai, China's top climate envoy, reiterated his country's view that developed nations had a moral obligation to make the more drastic cuts because they had prospered from decades of emissions.
He said China's only "quantified and measurable target" would be an aim to reduce energy consumption per unit of its gross domestic product by 20 per cent on 2005 levels by 2010.
Yvo de Boer, the executive secretary of the UN Framework Convention on Climate Change, admitted that there was currently little consensus on the necessary extent of cuts.
"We are not even at the stage yet where we have all the initial emissions reduction offers from all industrialised countries," he said.
John Prescott, the former deputy Prime Minister, who helped broker the Kyoto deal, warned rich nations would have to make more sacrifices.
"Copenhagen is a much more difficult nut to crack than Kyoto," Mr Prescott warned, adding rich countries faced having to make a "fundamental change" to their economies.