UN praises Pope's 'clarion call' for climate change action

In a radically worded letter addressed to every person on the planet, the leader of the world's 1.2 billion Catholics blames human greed and self-destructive enthralment to new technologies and progress for the critical situation Earth now finds itself in.

"This Encyclical is a clarion call that resonates not only with Catholics, but with all of the Earth's peoples. Science and religion are aligned on this matter: The time to act is now," UNEP chief Achim Steiner said in a statement.

Green activists have hailed the charismatic Argentinian pontiff's widely-trailed intervention as a potential game-changer in the debate over what causes global warming and what can be done to reverse it.

"We share Pope Francis' view that our response to environmental degradation and climate change cannot only be defined by science, technology or economics, but is also a moral imperative," the UNEP statement added.

"We must not overlook that the world's poorest and most vulnerable suffer most from the changes we are seeing. Humanity's environmental stewardship of the planet must recognise the interests of both current and future generations."

Environmentalists hope it will significantly increase the pressure for far-reaching measures to be agreed when more than 200 countries gather in Paris for a December summit aimed at clinching a global accord on carbon emissions.

"We have the opportunity to positively alter the course of history, creating a better and more equitable world for all," Steiner added.

"Given what we know about the state of our planet, and the choices we can make today, there can be no equivocating in the face of grave consequences."