It's a year since Pope Francis published Laudato Si' - On Care for our Common Home, the first papal letter devoted to the need to protect God's creation from environmental damage such as climate change.
Few 'encyclicals' (to use the official parlance) have provoked so much advance attention. Newspapers and broadcasters prepared lengthy coverage of the 40,000-word letter. Fossil fuel executives scripted their excuses. Even US presidential candidates took notice, with Catholic politicians Jeb Bush and Rick Santorum questioning the Pontiff's authority on 'issues of science' and urging him to stick to theology, seemingly unaware they were denouncing a theological tour de force.
In the encyclical, the Pope implored us to change the way we operate our politics, economies, and societies, arguing that the costs fall on people in the world's poorest communities. He called for a cultural revolution, in which we "regain the conviction that we need one another, that we have a shared responsibility for others and the world".
Laudato Si' was also extraordinary in that it was addressed to every person on the planet, rather than just the Catholic Church. And the world listened. Leaders from around the globe instantly welcomed what UN climate chief Christiana Figueres described as a clarion call. French President François Hollande stated his hope that "the special voice" of the Pope would be heard in all continents, not just by believers.
The Holy Father made no secret of his intention to influence the negotiations at the Paris climate change conference which followed the encyclical's release, praying for "a positive outcome to the present discussions, so that future generations will not have to suffer the effects of our ill-advised delays." Francis explicitly referred to the 1992 Rio Summit - a predecessor to Paris - which he described as prophetic for its time, but which had led to insufficient action.
The Pope intended that this time round would be different. Laudato Si' had a palpable presence from the start of the Paris Conference. Multiple heads of government cited it and praised it in their opening speeches. The UK government told CAFOD that the encyclical acted as "an important intervention which helped to create the momentum required to deliver an ambitious outcome" and the Ambassador to the Holy See Nigel Baker claimed with certainty that the document set the stage for the Paris Agreement. The result was an accord which launches a new era of action, committing us to preventing the loss of more homes, livelihoods, and lives to the changing climate.
Laudato Si' also had a profound impact on Catholics in the UK. Unprecedented interest was shown by parishioners across the country - politically, intellectually, and spiritually. More than 40,000 people signed a petition to the Prime Minister launched by CAFOD and our Scottish and Irish partners SCIAF and Trōcaire on the day of the encyclical's publication. This was added to 900,000 signatures gathered by the Global Catholic Climate Movement in the run-up to Paris. Nearly 8,000 copies of a guide to help people reflect on the encyclical have been ordered and hundreds of Catholics have attended study days we've organised around England and Wales. Perhaps most impressively, dozens of campaigners took the road to Paris to demand action - by train, by bike, or by foot - sometimes literally underneath a Laudato Si' banner.
A year on, there can be little doubt that Laudato Si' has had an extraordinary influence. This "astonishing an exceptionally rich document", as Helen Goodman MP described the encyclical in a Commons debate on the document, must become a blueprint for our interaction with nature, the development of our economies, and the operation of our societies. Our duty now is to ensure that its impact continues.