A coalition of churches has begun a campaign to curb climate change, by reducing emissions of greenhouse gases.
Cardinal Murphy O'Connor and Archbishop Hope lead the campaign
"Operation Noah" aims to highlight warnings that atmospheric warming from burning carbon fuels is altering climate patterns and raising sea levels.
The campaign is being organised on behalf of Churches Together in Britain and Ireland.
Lead figures include the Archbishop of York, David Hope, and the head of the Roman Catholic Church in England and Wales, Cardinal Cormac Murphy O'Connor.
They are urging people to change their lifestyles to burn less fossil fuel.
Delegates attending a conference in Coventry on Saturday to launch the campaign were asked to sign a covenant promising to cut their greenhouse gas emissions.
They were also encouraged to put pressure on the UK government and world leaders to do the same.
The conference was followed by a parade through Coventry and a speech by Dr David Hallman, co-ordinator of the World Council of Churches' climate change programme, at the city's cathedral.
Jonathon Porritt, chairman of the UK Sustainable Development Commission and director of Forum for the Future, said he was delighted churches were taking up the issue of climate change.
He said: "We could easily sleepwalk into an ever more dangerous future.
"Operation Noah is a wake-up call, not only to people of faith but to the whole of society.
"It makes us stop and think what we are doing to the earth and dares us to live by a new set of values."
BBC religious affairs correspondent Robert Pigott said the campaign was "the boldest co-ordinated step yet by senior church leaders to intervene in the political debate over climate change".
Archbishop Hope and Cardinal Murphy O'Connor said human development was standing at a crossroads on the brink of ruining a fragile environment.
Other church leaders backing the campaign include the Archbishop of Glasgow Mario Conti, David Kerr, Methodist Superintendent of the Belfast Central Mission, and Sister Eluned Williams, former President of Methodism in Wales.
In July, the Archbishop of Canterbury, Rowan Williams, said excessive use of fuel threatened the viability of humans as a species and threatened them with vicious conflict.
He called for a tax on greenhouse gas emissions.