A landmark conference on tackling climate change opened in Copenhagen on Monday, with negotiators from 192 countries aiming toward a deal to ward off global warming's potentially catastrophic effects.
The meeting will climax on December 18 with more than 100 heads of state or government in attendance.
Opening ceremonies began with a short film featuring children of the future facing an apocalypse of tempests and desert landscapes if world leaders failed to act today.
"There will be hundreds of millions of refugees," Rajendra Pachauri, head of the UN's panel of climate scientists, said in the film.
"Please help save the world," said a little girl, plaintively.
Danish Prime Minister Lars Loekke Rasmussen told opening ceremonies that the world is looking to the conference to safeguard humanity.
"The world is depositing hope with you for a short while in the history of humanity," Rasmussen said.
"For the next two weeks, Copenhagen will be Hopenhagen. By the end, we must be able to deliver back to the world what was granted us here today: hope for a better future."
After opening statements, negotiators from 192 countries were to embark on a gruelling round of talks under the UN Framework Convention on Climate Change (UNFCCC) before around 100 leaders attend a summit on December 18.
Delegates must craft a blueprint for tackling manmade "greenhouse" gases blamed for trapping solar heat and disrupting Earth's fragile climate system.
They must also put together a funding mechanism for helping poor nations most exposed to the potentially catastrophic effects of climate change.
If all goes well, world leaders will agree a political deal that sets down the course of action, including a roster of national pledges.
Further negotiations are expected to take place in 2010 to fill in the details. A legally-binding treaty would take effect from the end of 2012.
Analysts, though, stress the deep gap between the demands of developing countries and the willingness of rich countries to dig both into their pockets and into their carbon emissions.
US President Barack Obama is hoping to push through a new deal after the United States -- the world's biggest economy -- rejected Kyoto under his predecessor, George W Bush.
But the US Congress is still hammering out legislation to cut emissions, and Obama's opponents have been emboldened by a scandal over leaked emails from academics that they say raises questions on the science behind climate change.
The chief US negotiator in Copenhagen, Jonathan Pershing, blasted so-called Climategate as a non-affair and "opportunistic".
"It just happens to be the topic of the moment. It is a misrepresentation of the robustness of science," he said.
"... There are many data sets and they all show the same true type of change, (of) significant damages. I look at this and I think to myself, it's opportunistic."
Across the globe, 56 newspapers published the same editorial telling their leaders to agree on action to limit temperature rises to 2.0 degrees Celsius (3.6 degrees Fahrenheit) or risk seeing climate change "ravage our planet".
"We call on the representatives of the 192 countries gathered in Copenhagen not to hesitate, not to fall into dispute, not to blame each other but to seize opportunity from the greatest failure of modern politics," the editorial said.
The Copenhagen conference venue has been declared UN territory, with about 15,000 delegates, journalists and observers from grass-roots organisations attending.
Another 19,000 who registered will not be admitted, as the venue has reached capacity.
More than half of all of Denmark's police force has been deployed to the capital and police warned they would act swiftly to quell any violent protests.