 The biggest climate meeting in history, with 15,000 participants from 192 nations, begins in Copenhagen on Monday seeking to agree curbs on greenhouse gas emissions and raise billions of dollars for the poor in aid and clean technology. Campaigners say politicians have 2 weeks to save the planet from catastrophic climate change in the talks, which end with a summit of 105 world leaders -- including US President Barack Obama, on Dec. 18. The summit will have to overcome deep distrust between rich and poor nations about sharing the cost of emissions cuts. The attendance of the leaders and pledges to curb emissions by all the top emitters -- led by China, the United States, Russia and India -- have raised hopes for an accord after sluggish negotiations in the past two years. "Copenhagen is already a turning point in the international response to climate change," said Yvo de Boer, head of the UN Climate Change Secretariat. South Africa added new impetus, saying on Sunday it would cut its carbon emissions to 34 percent below expected levels by 2020, if rich countries furnished financial and technological help. World leaders did not attend when environment ministers agreed the existing UN climate pact, the Kyoto Protocol, in 1997. This time, in a Copenhagen conference hall with wind turbines outside generating clean energy, Danish Prime Minister Lars Lokke Rasmussen and Rajendra Pachauri, head of the UN's panel of climate experts, will be among speakers at Monday's opening session. Plans by world leaders to attend have brightened hopes since Rasmussen said last month that time had run out to agree a full legal treaty in 2009. The aim for Copenhagen is a politically binding deal and a new deadline in 2010 for legal details. British Prime Minister Gordon Brown, writing in the Guardian newspaper on Monday, said: "The British government is absolutely clear about what we must achieve. Our aim is a comprehensive and global agreement that is then converted to an internationally legally binding treaty in no more than six months." He added: "If by the end of next week we have not got an ambitious agreement, it will be an indictment of our generation that our children will not forgive." Some 56 newspapers from 45 countries including The Guardian, Le Monde, El Pais and Toronto Star on Monday published a joint editorial urging world leaders to take decisive action. "Humanity faces a profound emergency. Unless we combine to take decisive action, climate change will ravage our planet," it said. "The politicians in Copenhagen have the power to shape history's judgment on this generation: one that saw a challenge and rose to it, or one so stupid that we saw a calamity coming but did not avert it." A PINPRICK IN RISING TEMPERATURES The Kyoto pact binds industrialised nations to cut emissions until 2012 and even its supporters admit it is only a pinprick in rising world temperatures, especially since Washington did not join its allies in ratifying the pact. This time, the idea is to get action from all major emitters including China and India to help avert more droughts, desertification, wildfires, species extinctions and rising seas. The meeting will test how far developing nations will stick to entrenched positions, for example that rich nations must cut their greenhouse gases by at least 40 percent by 2020 -- far deeper than targets on offer. De Boer wants developed nations to agree deep cuts in greenhouse emissions by 2020 and come up with immediate, $10 billion a year in new funds to help the poor cope. He wants developing nations to start slowing their rising emissions. "It needs to be new money, real and significant," he said. De Boer said Pachauri on Monday would address a scandal about leaked e-mails from a British university that sceptics say show that some researchers exaggerated evidence for warming. But he said the UN process of reviewing climate science was well insulated against manipulation.