LONDON - Humanity faces a profound emergency and unless we combine to take decisive action, climate change will ravage our planet, a joint editorial published in newspapers in 45 countries said on Monday.

The 56 newspapers said they were taking the unprecedented step of speaking with one voice to implore world leaders to make the right choice at U.N. climate talks in Copenhagen.

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, the editorial read.

Two-weeks of talks open on Monday seeking to agree curbs on greenhouse gas emissions and raise billions of dollars for the poor in aid and clean technology.

The talks end with a summit of 105 world leaders, including U.S. President Barack Obama, on December 18 and must overcome deep distrust between rich and poor nations about sharing the burden of costly cuts in carbon emissions.

Climate change has been caused over centuries, has consequences that will endure for all time and our prospects of taming it will be determined in the next 14 days, read the front-page editorial.

It was published in 20 languages, including Chinese, Arabic and Russian, in newspapers including the Guardian in London, Le Monde in France, the Toronto Star, Gulf Times, Botswana Guardian and Miami Herald.

This should not be a fight between the rich world and the poor world, between east and west. Climate change affects everyone, and must be solved by everyone.

The science is complex, but the facts are clear. The world needs to take steps to limit temperature rises to 2C, an aim that will require global emissions to peak and begin falling within the next 5-10 years.

A bigger rise of 3-4C -- the smallest increase we can prudently expect to follow inaction -- would parch continents, turning farmland into desert. Half of all species could become extinct, untold millions would be displaced, whole nations drowned by the sea, it read.

The question is no longer whether humans are to blame, but how little time we have got left to limit the damage.

It urged politicians in Copenhagen to agree the essential elements of a fair and effective deal and a firm timetable for turning it into a treaty, saying next June's U.N. climate meeting in Bonn should be their deadline.

(Editing by Jeremy Laurence)