The warning is part of a joint letter sent by the Archbishop of Canterbury, Dr Williams, the Archbishop of the Church of Sweden, the Most Rev Anders Wejryd, and the Bishop of the EKD (Evangelische Kirche in Deutschland), Dr Wolfgang Huber.
In it, they warn, "Substantially reducing global emissions of greenhouse gasses will not avoid the serious impacts of climate change already experienced by many of the world's most vulnerable communities."
The letter has been sent to the President of the European Commission and the President of the Council of the European Union ahead of the Intergovernmental Conference on Climate Change in Bali from 3 to 14 December.
The Church leaders also called on world governments and the European Commission to "strengthen their commitment to addressing the challenge of climate change".
They echoed the concerns of numerous Christian humanitarian agencies including World Vision, Tearfund and Christian Aid, that the impact of climate change is being felt most severely by those who have done the least to cause it.
This, they say, makes the issue of a joined up response to climate change not simply a question of environmental good practice, but also of international justice.
"Climate change is not just about addressing environmental degradation; it is also about fighting poverty and providing for human security," they state. "The creation of new migration patterns from waterlogged, water scarce or food scarce regions will exacerbate existing vulnerabilities and lead to heightened regional and international security.
"Securing a just and equitable post-2012 treaty depends on governments progressing beyond notions of justice that reflect their own national interests to one that provides for the global common good."
