LEADERS in faith and science were united last week in praise of the encyclical letter Laudato Si' [God be praised]: On care for our common home, Pope Francis's "powerful intervention" on the degradation of the earth.

Among those welcoming the encyclical, published on Thursday of last week, was the head of the UN's environment programme, Achim Steiner, who said that it "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."

The head of campaigns at Friends of the Earth, Andrew Pendleton, said that the Pope had "shown impressive and inspiring leadership where many elected leaders have failed".

In Laudato Si' the Pope writes: "Many of those who possess more resources and economic or political power seem mostly to be concerned with masking the problems, or concealing their symptoms, simply making efforts to reduce some of the negative impacts of climate change." Nothing less than a "bold cultural revolution" will do, given that "we may well be leaving to coming generations debris, desolation, and filth."

Although he acknowledges that business is a "noble vocation, directed to producing wealth and improving our world", and says that he is not anti-modernity - "Nobody is suggesting a return to the Stone Age" - he is scathing about the bail-out of the banks and "short-sighted approaches to the economy, commerce, and production".

The most one can expect of this powerful group, he writes, is "superficial rhetoric, sporadic acts of philanthropy, and perfunctory expressions of concern for the environment, whereas any genuine attempt by groups within society to introduce change is viewed as a nuisance based on romantic illusions, or an obstacle to be circumvented".

To those in favour of population control he says: "To blame population growth instead of extreme and selective consumerism on the part of some, is one way of refusing to face the issues"; and he gives a critique of modern ills, including a prevalent "throwaway culture" and "rampant individualism".

Although the document states that the Roman Catholic Church "does not presume to settle scientific questions", the Pope refers to a "very solid scientific consensus" about global warming, and to studies suggesting that it is mostly caused by human activity. Fossil fuels must be "progressively replaced without delay", he writes.

Greenpeace's international executive director, Kumi Naidoo, called the encyclical "a welcome rebuke to climate-change deniers and the interests that seek to thwart progress. . . The Pope's words should jolt heads of government out of their complacency, and encourage them to bring in tough laws in their own countries to protect the climate, and to agree a strong climate protocol in Paris at the end of this year."

Christians in Science welcomed the work as a "powerful intervention", informed by "the very distinguished atmospheric scientists in the papal academy".

Anglican leaders welcomed the Pope's intervention. The Archbishop of Cape Town, the Rt Revd Thabo Makgoba, gave examples of the effects of climate change already seen in Africa and developing countries, including floods in Mozambique and droughts in Namibia.

"In drawing attention to the high levels of consumption, greed, and wastefulness in our world . . . the encyclical makes clear that we need to adopt simpler, more wholesome lifestyles," he said.

Other Christian groups added cautionary notes to their welcome for the encyclical. The chairman of the charity Green Christian, Paul Bodenham, said that it was vital that it spurred reform of Catholic Social Teaching, which "has developed in an ecological vacuum, and is simply not fit for the 21st-century predicament". The charity is critical of the "technocratic notion of 'stewardship of creation'".

A divestment campaigner at Operation Noah, Ellie Roberts, expressed a hope that it would "inspire Catholic communities around the world to look at how their own investments might be financing climate change".

The head of international climate politics at Greenpeace, Martin Kaiser, said that he hoped that the Vatican bank would divest from coal, oil, and nuclear power and support renewables. Others gave examples of work already under way to implement the Pope's call to action.

Christian Aid's principal Climate Change Adviser, Dr Alison Doig, gave examples of work by its partners, including the use in Malawi of improved stoves to reduce deforestation, and flood-warning systems in the Philippines.

But Jeb Bush, the Republican presidential candidate in the United States, said: "I hope I'm not going to get castigated for saying this by my priest back home, but I don't get economic policy from my bishops, or my cardinal, or my pope."

The venue for the UK launch was Our Lady and St Joseph's Catholic Primary School, in Poplar, east London, which opened in September last year. It has been constructed from timber and brick, and uses solar energy. It is in one of the most deprived parts of the country, near Canary Wharf and the country's financial epicentre.

The President of the Catholic Bishops' Conference of England and Wales, Cardinal Vincent Nichols, said that the document contained enough to "disquiet some people behind me".

Laudato Si': a digest by the Bishop of Sheffield, Dr Steven Croft

THE Pope's encyclical letter is addressed to the whole of humankind, not only Roman Catholics, and not simply Christians. He writes: "I wish to address every living person on the planet."

His plea is for the whole human family to come together at this key moment in our history to seek sustainable development across the earth. The letter describes what is happening to our common home, and draws out the clear consequences for human life.

All of these developments disproportionately affect the poorest nations. The poor should be at the heart of our concern for the environment, and the two cannot be separated.

Chapter Two of the letter sets out a clear and detailed basis for Christians (and others) to renew their commitment to the earth, rooted in scripture and the doctrine of creation.

Chapter Three explores the human roots of the ecological crisis. Our technical prowess has brought us to a crossroads. We have placed ourselves at the centre of the universe, as masters of creation, and failed to understand what life is for.

A better and more profound understanding is needed. We are not isolated individuals, but part of the larger universe, and in a particular place within it.

In Chapter Four, the Pope explores environmental, economic, and social ecology, cultural ecology, and the ecology of daily life. Environmental degradation is a consequence of the human condition, not an accident of it.

In Chapter Five, he turns to lines of approach and action. These are to be rooted in Christian hope, and the expectation that things can change. He highlights the importance of dialogue on the environment in the international community, and the forthcoming climate-change conference in Paris, but also the need to bring economics politics, science, and religions into conversation at a local level.

In the sixth and final chapter, the letter turns to what we ourselves can do. We are to be partners, not observers, in this conversation.

Lifestyle is key, as we each learn to live sustainable lives. Education is vital in schools, homes, and seminaries. He uses the term "ecological conversion"; part of our discipleship is recovering our responsibility to the earth.

But individual action is not enough. Love must lead us to political action as well, to act in hope to renew the mindset of the world, and reform our stewardship of the earth.

The encyclical letter Laudato Si' can be found on the Vatican website