Delegates from 192 countries have got down to work at the UN climate summit in Copenhagen, heartened by the declaration from the US that greenhouse gases threaten human health.
It is not just government representatives who are in the Danish capital, the conference is a magnet for a variety of protest groups.
It is hoped that world leaders will be able to deliver an ambitious and workable climate change agreement.
UN Executive Secretary Yvo de Boer said there was no time to lose: “Basically negotiators now have six days until ministers arrive. Once those ministers arrive they will have two days before the heads of state and government arrive.
“So my challenge to people is get the basic work done in the first week, make sure that the foundation stones are in place, make sure that we have clarity on what needs to be done on adaptation, mitigation, technology, finance, capacity building and forest to insure that action begins when the Copenhagen conference is over.”
Environmentalists have launched a mock award, the Angry Mermaid Award, for the biggest negative influence in the coming talks.
The sheer size of the measures needed, and the divisions between rich and poor nations, mean many fear a UN pact may be put off in favour of a less binding declaration.