Pope Francis warned that the world is heading for “unprecedented destruction” unless mankind confronts climate change and reforms the way it treats the planet, as the most eagerly anticipated papal document in living memory was leaked.

In a 192-page encyclical on global warming that looks set to define his tenure, the Pope paints an apocalyptic picture in which the world’s poorest are the biggest victims of a web of environmental, human, financial and ethical degradation that puts the entire planet at risk.

In an extraordinarily frank document, the Pope lambasts rich countries for “looting” the world and takes aim at bankers and climate sceptics for accelerating its decline.

He warns that the world is facing widespread crop failure, economic ruin, mass migration and the destruction of entire eco-systems.

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“If the current trend continues this century we could witness climate change unlike anything seen before and the unprecedented destruction of eco-systems, with serious consequences for all of us,” he writes.

Pope Francis has spent months working on the encyclical, the contents of which has been the subject of eager anticipation in the Vatican and environmental circles. It is the encyclical, or papal letter, aimed at everyone in the world, regardless of religion.

Environmentalists hope his strident warnings will encourage right-wing climate sceptics - particularly US Christians - to rethink their position.

Global average temperatures will reach about 4C higher than pre-industrial times by 2100, according to predictions (Getty) (Getty Images)

“Climate change is a problem with serious implications for the global environmental, social, economic, distribution [systems] and policies and constitutes one of the main current challenges for humanity,”

The Vatican reacted with fury to the leak on Monday night, accusing the magazine responsible “heinous act” that amounted to “sabotage against the pope”.

In the encyclical, titled “Laudato Sii”, or “Praised Be”, the Pope quotes Patriarca Bartolomeo of the Eastern Orthodox Churchas as saying: “A crime against nature is a crime against ourselves and a sin against God”.

And he is withering about the financial system.

“The economic powers shall continue to justify the current world system, in which speculation and and the aim for financial returns to prevail that tend to ignore each context and the effects on the environment and on human dignity. So clearly it reveals that environmental, human and ethical degradation are intimately connected,” he wrote.

Although the first ever encyclical on the environment concentrated heavily on the natural world, the pope repeatedly linked climate change with the plight of the poor.

“The warming caused by the enormous consumption of some rich countries has repercussions in the poorest places on earth, especially in Africa, where the increase in temperature, combined with drought, has had disastrous effects on the performance of crops,” the pope wrote.

Cost of climate change (DARA)

Pope Francis is also extremely concerned about the prospect of mass migration of animals, plants and humans as global warming means they cannot function in their traditional habitat.

He calls for a new global political authority tasked with tackling the reduction of pollution and the development of poor countries and regions.

Although he accepts that there may be some natural causes of global warming, the pope lays most of the blame for climate change squarely at the feet of mankind.

“Humanity is called to take note of the need for changes in lifestyle and changes in methods of production and consumption to combat this warming or at least the human causes that produce and accentuate it,” he wrote.

The pope is very critical of anybody who stands in the way of tackling the problem of global warming – whether they are merely indifferent or actively sceptical.

“The attitudes that stand in the way of a solution, even among believers, range from negation of the problem, to indifference, to convenient resignation or blind faith in technical solutions,” he wrote.

According to research, climate change is set to unleash a series of decades-long 'megadroughts' this century (Getty)

The letter to the world’s 1.2bn catholics is aimed at influencing the debate ahead of crucial United Nations talks in Paris in December at which world leaders have pledged to agree decisive action to curb global warming. The pope hopes that adding a moral dimension to the scientific arguments – together with the support of the huge number of Catholics around the world – will raise the ambition of world leaders to agree a meaningful deal at the talks.

The encyclical is likely to anger some sections of America, who are sceptical about the presence of climate change and mankind’s role in it.