The U.K. has cleaner beaches and natural protection and shouldn't risk the environment by leaving.
An early start date would lock a U.S. president into the deal for four years.
Republicans didn't even wait for a global climate change deal to be struck in Paris to start undermining it.
Paris should come up in tonight's debate, if only to ask Republicans about the backlash to their proposal to pull out of the deal.
Americans "can be proud because this historic agreement is a tribute to American leadership," president says.
Will the Paris Agreement be enough?
"Our responsibility to history is immense," French Foreign Minister Laurent Fabius said.
The sticking points have been finance, pace and ambition.
A host of Californian political and business leaders are Paris to tout their state's success as a carbon-slashing powerhouse.
The Democratic presidential candidate is using crunch week of COP21 to try to upstage rivals Hillary Clinton and Martin O'Malley.
Republicans in Congress need to "just sit down, and forget about politics," Jane Goodall said.
Oceans produce most of the oxygen we breathe, and they are threatened by climate change.
An estimated 200 million people may be displaced by 2050. So far there's no plan to help them.
After just a few days, billions of dollars have been committed to clean energy.
Some of the event's sponsors might be part of the problem, not the solution.
We've been waiting years for this moment, says Ken Berlin, president of Al Gore's Climate Reality Project. Let's make it count.
A translation of diplomat-speak to commoner language, focusing on why everyone's in Paris and what it all means.
Although the toughest work is already done, that doesn't mean we won't see a lot of fights.
Public protests were banned after the deadly attacks in Paris.
Authorities use emergency laws put in place following the Paris shootings.