Leaders of churches in Britain including the Archbishop of Canterbury and the head of Scotland's Roman Catholics have made a Lenten call for repentance and a "change of direction" to combat the dangers of climate change.
Rowan Williams has joined Cardinal Keith O'Brien, Archbishop of St Andrews and Edinburgh, among other church leaders, in signing a declaration which says reducing dependence on fossil fuels is "essential" to Christian discipleship.
"Continuing to pollute the atmosphere when we know the dangers goes against what we know of God's ways and God's will," it said.
"We are failing to love not only the earth, but our neighbours and ourselves, who are made in God's image. God grieves over the destruction of creation and so should we."
The declaration was released by Operation Noah, the Christian environmental charity. Other signatories include Bishop of London the Rt Rev Richard Chartres, Archbishop of Wales Barry Morgan and leaders of the Methodist, Baptist and United Reformed churches.
Archbishop Desmond Tutu, former archbishop of Cape Town, South Africa, has also signed the declaration.
The Rt Rev David Atkinson, of Operation Noah, said: "We believe that this is a time of urgency for the church.
"The threat of runaway climate change is the most significant moral question facing us today."
The launch declaration comes on Ash Wednesday, the start of Lent, traditionally a period of penitence, prayer and reflection for Christians in the run-up to Easter. The declaration will be marked by a service in central London this evening.