"Should good Christian people be on marches with big placards?" Dowd asked.

"In a word, yes," Williams replied.

Williams has repeatedly spoken of his hopes for the summit, devoting his Advent message to the conference. Unlike his 2008 Advent message, a theological reflection on waiting and longing for the birth of Jesus, Williams shorter 2009 video focuses upon hope for environmental preservation.

"One of the things that we ought to be able to ask ourselves in Advent is 'what is it that we most deeply hope for?'" Williams asked, explaining that this Advent he will be going to Copenhagen to speak "at the great gathering there which will be discussing environmental issues and governments' response internationally to them."

"I want to be there and I want the church to be there witnessing, not just to a political program, not just to a damage limitation exercise which will minimize the evil results of our lifestyle, but witnessing to God's purpose and God's hope," the British cleric said. "Witnessing to what God is about in creation, our own creation as well as the creation of the world around us. So, during this Advent, let your prayers be in that direction."

Williams also spoke during an address to demonstrators, as well as at the Lutheran cathedral in Copenhagen, where the Danish Council of Churches invited the leader of the world's 77 million Anglicans to preach.

Draped with a massive banner that read "Time for Climate Justice," the Church of Our Lady drew ambassadors, members of international delegations and the Queen of Denmark for the ecumenical service.

Williams' sermon called the conference participants to "act for the sake of love" in the face of fear, which could leave "a world of utterly chaotic and disruptive change, of devastation and desertification, of biological impoverishment and degradation."

"If there is any 'fear' around here, it should be fear of spoiling the heritage given us, of forgetting the overwhelming scale and depth of the gift and of our responsibility to care for it," Williams said.

The Archbishop said the people were not doomed to carry on "in a downward spiral of the greedy, addictive, loveless behavior that has helped to bring us to this point." However, Williams said that fear still ruled hearts and imaginations.

"We have not yet been able to embrace the cost of the decisions we know we must make. We are afraid because we don't know how we can survive without the comforts of our existing lifestyle."

"Ask how the policies you follow and the lifestyle that you take for granted look in the light of the command to love the world you inhabit," Williams said. "Ask what would be a healthy and sustainable relationship with this world, a relationship that would in some way manifest both joy in and respect for the earth. Start with the positive question - how do we show that we love God's creation?"

While Williams' words seemed targeted primarily at developed nations, asking them to accept a change in their standard of living, he also indicated that actions taken by wealthy nations with the goal of preempting climate change could also negatively impact poorer countries.

"How shall we build international institutions that make sure the resources get where they are needed - that, for example, 'green taxes' will deliver more security for the disadvantaged, that transitions in economic patterns will not weigh most heavily on those least equipped to cope?" Williams asked.

While Williams spoke in measured tones about his hopes for the conference, Tutu displayed his signature fiery persona as he spoke before demonstrators in the Danish capital.

"We know that over 300,000 people around the world are dying as a result of all of the poverty caused by the emissions that have come from the rich countries," Tutu exclaimed. "Hello, rich people. Hello there, hello America."

The Nobel Peace Prize laureate then presented a petition of 512,894 signatures to Yvo de Boer, the United Nations' top climate official, who represented summit delegates.

"Persuade them to be smart like you," said Tutu, as he handed the petition to de Boer, according to a report by Ecumenical News International.

---Jeff Walton writes for the Institute on religion and Democracy. He is based in Washington, DC