Addressing the 21st Conference of the Parties (CoP-21), Obama said: "I have come here personally, as the leader of the world's largest economy, and the second largest emitter to say that the US not only recognises its role in creating this problem (of emissions), we embrace our responsibility to do something about it."
The US will reduce its carbon emissions 26-28 percent below the 2005 levels within 10 years, Obama said.
Obama's speech was longer than 13 minutes, and the president ignored the repeated beeps, which indicated over-time.
He said world leaders must "reaffirm" their commitment to joint effort for public and private investment for green energy globally.
Nearly 150 global leaders have gathered here for this crucial UN climate meet that will continue till December 11, where a possible new global agreement on climate change would be discussed.