CANCUN, Mexico (Reuters) - Almost 200 nations at U.N. climate talks in Mexico must compromise on a modest package of measures or face escalating damage from floods, droughts and rising seas, scientists and politicians said on Monday.
"Our relation with nature is reaching a critical point," Mexican President Felipe Calderon told the opening of the two-week talks in a tightly guarded hotel by the Caribbean with warships patrolling off the coast.
"We either must change our way of life to stop climate change or climate change will permanently alter the way of life of our civilization, and it will not be for the better," he said.
The talks of almost 200 nations will seek to break deadlock between rich and poor -- especially the United States and China -- on ways to slow climate change since the U.N.'s climate summit in Copenhagen last year failed to agree a binding treaty.
The United Nations wants agreement on a new "green fund" to help developing nations and ways preserve rain forests and help the poor adapt to a hotter world. It will also seek to formalize existing targets to curb greenhouse gas emissions.
Calderon said that extreme weather including storms in Mexico, floods in Pakistan and a heatwave in Russia in 2010 showed a need for compromise to pave the way to more action.
"Delays in action would only lead to impacts which would be much larger and in all likelihood more severe than we have had so far," Rajendra Pachauri, head of the U.N. panel of climate scientists, told an opening ceremony of the two-week meeting.
He said costs of containing global warming would rise the longer the world waited.
The talks are seeking to find a successor to the U.N.'s existing Kyoto Protocol, which obliges all rich nations except the United States to cut greenhouse gas emissions by an average of 5.2 percent below 1990 levels by 2008-12.
Kyoto backers say they will only deepen their cuts, shifting from fossil fuels to clean energies such as wind or solar power, until 2020 if the United States and big emerging economies led by China and India take on binding curbs.
But developing nations say they need to burn more energy, pushing up greenhouse gas emissions, to fight poverty. President Barack Obama's hopes of legislating greenhouse gas cuts have vanished after Republican gains in mid-term emissions.
At the opening ceremony, Christiana Figueres, head of the U.N. Climate Change Secretariat, mentioned the word "compromise" four times in a short speech urging a "balanced outcome."
"A tapestry full of holes will not work and the holes can only be filled in through compromise," she said, adding she was convinced a deal was possible.
Success would help get the talks back on track after the acrimonious Copenhagen summit agreed only a non-binding deal to limit a rise in world temperatures to 2 degrees Celsius (3.6 F) above pre-industrial times.
Failure would raise questions about the future of Kyoto, which underpins prices in carbon markets. Kyoto will expire at the end of 2012 if it is not extended, leaving a patchwork of only national measures to combat climate change.
In Brussels, U.N. climate commissioner Connie Hedegaard said that the talks risked "losing momentum and relevance" if they failed to reach a deal.
She said that it was regrettable that some other countries seemed unable to move forwards -- noting that the United States had failed to legislate cuts.
Jonathan Pershing, head of the U.S. delegation at the Cancun talks, told Reuters that Washington was willing to "move forward" on all issues such as finance or forestry protection in Cancun "in the context of a package."
Separately, a report by Oxfam said that more than 21,000 lives have been lost to climate related disasters in the past year alone.
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