Last Updated Nov 30, 2015 7:45 PM EST
PARIS -- President Obama made a strong pitch on Monday for an international deal to cut carbon emissions linked to climate change.
In Paris, he paid tribute to the 130 killed in the recent attacks -- and said the climate talks are an act of defiance against terrorists. Nearly 150 heads of state are attending -- the largest group of world leaders ever to stand together.
"I've come here personally, as the leader of the world's largest economy and the second-largest emitter, to say that the United States of America not only recognizes our role in creating this problem, we embrace our responsibility to do something about it," Mr. Obama said.
Mr. Obama came to office promising to slow climate change. On Monday, he pressed China and India, the world's other top polluters, to join him.
Mr. Obama offered to help poorer countries convert to clean energy. The goal is to get 147 countries to reduce carbon emissions enough to keep global warming below 3.6 degrees Fahrenheit. That's the level some scientists believe would prevent natural disasters like floods and droughts.
Mr. Obama said those types of events are a risk to global security, and praised France for hosting the summit just two weeks after the terror attacks.
"What greater rejection of those who would tear down our world than marshaling our best efforts to save it?" Mr. Obama said.
The world's biggest carbon emitter is China. And right now the capital is choking. CBS News' Seth Doane reports on a polluted day like Monday, Beijing is limiting activities at factories and construction sites. And it is also encouraging people to stay indoors.
China launched a so-called war on pollution -- which it appears to be losing. Two-thirds of China's energy comes from coal. Heating systems make pollution even worse.
The government has blamed the pollution on high humidity and a lack of wind. CBS News found many people on the streets weren't wearing masks either because they questioned the value of wearing one -- or simply as a sign of resignation.
Another growing threat to the environment is the Earth itself. A spectacular amount of Methane, one of the worst heat trapping gases, has been locked up in the world's frozen tundra -- until now.
CBS News' Mark Phillips reports from above the Arctic Circle in Svalbard, Norway. This isn't just a scientific frontier, it's polar bear country. Instruments scientists are using are measuring a worrying trend that's happening now.
What the instruments are showing is that greenhouse gasses that scientists used to believe were trapped forever in the frozen arctic ground are now being released.
The worry is that with arctic temperatures rising more quickly than anywhere else, the gases may be escaping at an increasing rate. And the more greenhouse gasses, the more global warming.