Biggest-ever UN climate talks to open

A UN conference on climate change is set to begin in Copenhagen, Denmark a few hours from now. More than 15-thousand people, including delegates from 192 countries, will attend the biggest UN climate meeting in history.

An alert, a faux melting iceberg in front of the Danish parliament.

Posters about climate change. Tight security on roads leading to the venue.

Copenhagen is ready for the two-week event, the biggest-ever UN climate talks.

On the eve of the gathering, the UN's top climate chief warns the time is now to agree on the outlines of a tougher climate deal.

Yvo De Boer, UN Framework Covention on Climate Change, said, "The scientific community told us we have a five-to-ten year window of opportunity to turn the upward emission trend into a downward emission trend. That is why we have to act now."

The upcoming climate talks aim to hammer out a new agreement to curb global warming, and replace the 1997 Kyoto Protocol.

A key issue is cutting greenhouse gas emissions.

Scientists blame the excess amount of carbon dioxide in the earth's atmosphere, for raising average global temperatures over the past decades.

The UN says rich nations must accept deep cuts in their emissions by 2020.

They will also seek deals on how much financial assistance rich countries should provide, to help poor nations deal with climate change.

De Boer says the Copenhagen summit has to deliver three things.

Yvo De Boer, UN Framework Covention on Climate Change, said, "What I want to see at the end of this conference is a list of rich country targets that are ambitious, clarity on what major developing countries will do to limit the growth of their emissions and a list of financial pledges that will make it possible for the much broader developing nation community both to change the direction of their economic growth and adapt to the inevitable impacts of climate change."

UN officials say greenhouse gases must be reduced by 25 to 40 percent by 2020 to below 1990's output, to keep temperatures from rising in the less dangerous range of 2 degrees Celsius.