Officials from 192 countries that share our planet are trying again to protect it from climate change trends that worry some scientists. Environment ministers and other government leaders are in Copenhagen, capital of Denmark in Europe, for a United Nations conference on global warming that runs through Dec. 18. President Obama plans to attend, as do more than 85 other national leaders.

It's part of a long-term struggle to balance environmental and economic policies. Most experts believe "greenhouse gas" emissions from burning coal and oil in factories, vehicles and utility plants should be reduced to slow or halt a rise in average atmospheric temperatures. This global warming could bring floods, droughts, coastal erosion and food shortages as polar ice caps melt.
Alternative fuel advocates say research and development of new power sources would bring economic as well as environmental benefits by creating new industries and jobs. Skeptics question the scientific projections and economic impact.

The Obama administration says he'll present a U.S. target for reducing carbon dioxide emissions in the years and decades ahead. One of the toughest hurdles in Copenhagen will be reaching agreement among industrialized countries and developing nations such as India and China over who should cut, by how much and who should pay for it. Some emerging countries resist energy use restrictions that could limit their growth.
The UN's climate chief suggests a two-stage process of agreeing this month on an outline for a more formal agreement to be considered late next year.

U.S. senator says: "You'll never convince me that America cannot have the cleanest air and the purest water of any place on the planet. If Congress does not act soon, the world will leave us behind." -- Sen. Lindsey Graham, R-N.C.

Environmental leader says: "Now is the time for people to speak up and tell our leaders that yes, we want to solve global warming. We want to create green jobs, reduce our reliance on dirty fossil fuels, and produce the next generation of clean energy technologies." -- Frances Beinecke, president, Natural Resources Defense Council

European official says: "Complexity is no excuse for complacency. . . . If the whole world comes to Copenhagen and leaves without making the needed political agreement, then . . . it's the whole global democratic system not being able to deliver results in one of the defining challenges of our century." -- Connie Hedegaard, Danish minister for climate and energy