GWEN IFILL: We turn our attention now to this week's big meeting in Copenhagen on climate change and a new decision from the Obama administration.
NewsHour correspondent Kwame Holman begins with more about the meeting in Denmark.
KWAME HOLMAN: Diplomats from 192 nations gathered in Copenhagen today for the largest and potentially most important U.N. climate change conference ever, their goal, to shift away from fossil fuels and get rich countries to send billions of dollars to poorer ones to help them adapt.
Organizers warned, this could be the critical last chance to curb global warming.
CONNIE HEDEGAARD, president, United Nations Climate Change Conference: The science has never been clearer. The solutions have never been more abundant. Political will has never been stronger. And, let me warn you, political will never be stronger. This is our chance. If we miss this one, it could take years before we get a new and better one, if we ever did.
KWAME HOLMAN: U.N. climate leaders are seeking a global pledge to cut emissions worldwide 25 percent to 40 percent by 2020. They called on the conferees not to be put off.
YVO DE BOER, executive secretary, United Nations Framework Convention on Climate Change: The time for formal statements is over. The time for restating well-known positions is past.
KWAME HOLMAN: President Obama has called for a 17 percent reduction in U.S. emissions by 2020 from 2005 levels and an 83 percent cut by 2050. China and India also talked of cutting carbon dioxide emission rates by 25 percent to 45 percent.
MAN: It's hot in here.
CROWD: There's too much carbon in the atmosphere!
KWAME HOLMAN: Climate activists, such as these students outside the conference, also were trying to raise awareness. A woman from Fiji tearfully handed in a petition signed by 10 million people asking negotiators to help countries like hers.
LEAH WICKHAM, climate activist: We need a deal that is fair to the poorest people and nations, nations that have had little or nothing to do with the issue, but that will be affected the most.
KWAME HOLMAN: And, in Washington, the Environmental Protection Agency formally declared greenhouse gases are endangering public health, paving the way to regulate them.
Later, President Obama met privately with former Vice President Al Gore, who has lead the drive for climate action. The president will attend the conclusion of the Copenhagen conference on December 18.