Obama will attend a United Nations climate summit where he will announce new US commitments, aiming to ramp up the pressure on other major polluters like India and China to demonstrate they're not laggards in the global campaign against climate change.
White House officials said the US will offer tangible contributions such as American technology to help vulnerable populations deal with food security, sea level rise and other negative effects of climate change.
Obama had hoped to focus in his second term on legacy-making projects like curbing climate change. But a dizzying array of global crises has competed for his attention, overshadowing many goals he had hoped to achieve.
Over just a few days at the UN, leaders will be wrangling with deep problems in Ukraine, Iraq, Syria, Iran and Israel, to name a few.
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By taking time out at the UN for climate change, Obama is working to keep the issue at the top of the global agenda even after the crises of the day recede from memory.
The last time Obama gathered with so many leaders to discuss climate change was five years ago in Copenhagen, where a UN summit intended to yield a strong accord on emissions ended in failure.
That outcome dampened hopes that developed and developing nations could come together to address climate change in any serious way before temperatures spiral out of control.
Obama can't afford another failure in 2015. The talks already underway under the UN umbrella mark the last major opportunity for Obama to leave his imprint on the global response to climate change before his term ends and another president takes over -- potentially a Republican who would be less inclined to press the issue.