Although Vatican officials warned that the text was not final, it nonetheless offered a clear and detailed picture of the 78-year-old Argentine pontiff's message on the environment, which could emerge as the most enduring legacy of his tenure at the helm of the 1.2 billion-strong Catholic Church.
In the encyclical, which is timed to bolster the push for a global deal to cut carbon emissions in Paris at the end of 2015, Pope Francis writes that global warming has been caused "mainly by human activity", even though other factors, such as changes in orbits and the eruption of volcanoes may have played a role.
He laments that so far efforts to forge solutions to the "environmental crisis" have been stymied by "the refusal of the powerful, [and] the disinterest of the others".
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"The attitudes that are blocking solutions — even among believers — range from denial to indifference to comfortable resignation or blind faith in technology," he says.
"Many of those who hold more resources and economic or political power seem to focus mainly on disguising problems and hiding their symptoms, and are merely trying to mitigate the negative impacts of climate change," Pope Francis writes, adding that "speculation" and the "search for a quick profit" tend to ignore environmental impacts.
"The submission of politics to technology and finance is proven by the failure of global summits on the environment," he said.
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But Pope Francis is also calling on ordinary people — and not just Christians — to take action in their everyday lives. "Humanity must be conscious of the need to change its way of living, producing, and consuming," he writes.
Meanwhile, the leak of the text itself caused significant drama and debate in the city-state. La Stampa, an influential Italian newspaper, reported that within the Vatican it was seen as the work of conservative factions within the Holy See who were trying to undermine the Pope.
"There was a double aim: to weaken the message of the encyclical, which harshly criticises the environmental policies of hegemonic countries in certain points, and to attack the image of the pontiff as they resist his renewal of the Church," La Stampa wrote.
Climate change sceptics, particularly in the US, have taken aim at Pope Francis, who is due to address the UN and the US Congress on sustainable development in September.
US Republican presidential candidate Rick Santorum, a Catholic and climate change sceptic, has said the Church would be "better off leaving science to the scientists".