Calls for climate action at UN

Addressing the UN in New York Tuesday, Obama said the US would participate in alliances launched at the summit, including working with emitters such as petrol and agriculture companies. More than 120 world leaders are attending the one-day summit for countries, cities and businesses to discuss nonbinding pledges and announce commitments to reduce the impacts of global warming.

"This time we need an agreement that reflects the economic realities in the next decade and beyond," Obama said. He added that "the urgent and growing threat of climate change" would "define the contours of this century more dramatically than any other" issue.

At the meeting, international leaders hope to build momentum for a deal on reducing greenhouse gas emissions ahead of a conference in Paris in December 2015. Opening the meeting, UN Secretary-General Ban Ki-moon (pictured) told attendees that the world needed "all hands on deck" and had never before faced "such a challenge, nor such an opportunity."

"We are not here to talk," Ban said. "We are here to make history."

'Humankind's greatest challenge'

One recent report warned that a surge in carbon dioxide levels had pushed greenhouse gases to record highs, increasing in 2013 at their fastest rate in 30 years. Threats like this helped lead Leonardo DiCaprio, the UN's new climate ambassador, to bring star power to Tuesday's summit, urging world powers to stop ignoring the issue.

"As an actor, I pretend for a living; I play fictitious characters often solving fictitious problems," DiCaprio told the summit on Tuesday. "I believe mankind has looked at climate change in that same way - as if it were fiction." Sporting a ponytail and suit and tie, the star of "The Wolf of Wall Street" and "Titanic" added: "Now it is your turn. The time to answer humankind's greatest challenge is now. We beg of you to face it with courage and honesty."

Despite the summit's star-studded lineup, snubs from the leaders of China, the world's biggest polluter, and India, the No. 3 carbon emitter, have cast a cloud over the event. And, on Tuesday, Brazil, another member of the BRICS emerging-markets alliance, chose not to join the more than 150 countries that agreed to set the first-ever deadline to end deforestation by 2030.

That has put into doubt whether the United Nations can limit global warming to 2 degrees Celsius (3.6 F) over pre-industrial levels. Scientists say current emission trends could hike temperatures to more than twice that level by century's end.

Over the weekend, activists worldwide protested government and business leaders' inaction on climate change. On Monday, the group Flood Wall Street took to New York's financial district to demand that big businesses, which have long expressed official skepticism over climate change, own up to their roles in environmental destruction.

mkg/ng (Reuters, AFP, dpa, AP)