Christians concerned about climate justice will be among the thousands of campaigners expected to march in London on the eve of critical international climate change talks in Nairobi.

They will join the march this Saturday leading to the I Count rally in Trafalgar Square, organised by the Stop Climate Chaos coalition.

The Bishop of London, the Rt Rev and Rt Hon Richard Chartres, will preach at a special Service of Challenge, Commitment and Blessing at Grosvenor Chapel.

The service has been organised by Operation Noah - a Christian environmental movement set up by Churches Together in Britain and Ireland and Christian Ecology Link.

The congregation will hear the bishop preach on the issues of the day before he leads them to a rally in Grosvenor Square, ahead of the march to the Stop Climate Chaos gathering in Trafalgar Square.

This week saw the publication of the highly anticipated Stern Review on the Economics of Climate Change which set out the risks of climate change for the world's poorest and most vulnerable people.

Bangladesh is just one of many poor countries facing increased disease, floods and famine. The Bishop of Bangladesh, the Rt Rev Bishop Michael S. Baroi, has sent a message to be read at the Operation Noah service in which he warned: "One very simple truth about Global Warming is this; that it will spare nobody, however rich, mighty and powerful we think we are."

He continued: "Mr Tony Blair, the Prime Minister of the UK, once said that without proper action now, the average global temperatures would rise by 2 degrees Celsius. Scientists estimate that the subsequent rise in the sea level would be enough to swamp a large proportion of Bangladesh in 30, 40 years time. It would be a serious catastrophe for my country and for the whole region if much of the land in Bangladesh disappears under the sea.

"I become frightened to think that my grandchildren...will have no place to live on this planet earth. I really want to be sure that my grandchildren and their children after them will be able to enjoy the beauty of my country that I have enjoyed, and be able to have enough land to live, and enough land for food."

Bishop Baroi has appealed to campaigners attending the I Count event to continue the fight against global warming "for the sake of my country, my people and for the world at large".

"The UK government and the people should raise their voice in such a way that the people in the USA, China and India hear them and pursue their government to sit together to find some solutions to the problem," he said.

Methodist Church Secretary for International Affairs, Steve Hucklesby, will also be among speakers at the Operation Noah service.

He said: "The Stern Review stresses the need for strong action within the next 10 to 20 years. All countries have a part to play but developed countries, who are responsible for the bulk of emissions today, have a duty to lead the way. Operation Noah urges everyone to commit themselves to tackle climate change.

"We need to take practical actions to reduce emissions such as switching to green electricity but must also lobby politicians to act."

See www.stopclimatechaos.org and www.icount.org.ukfor more information on the day's events:
11.15am Service of Challenge, Commitment and Blessing at Grosvenor Chapel, 24 Audley Street, London
12 noon rally in Grosvenor Square. Speakers include the Bishop of London.
12.30 to 1.15pm service at St Martin-in-the-Fields Church, organised by Tearfund.
12.45pm march from Grosvenor Square to Trafalgar Square
1pm rally in Trafalgar Square.