World Leaders and Activists Express New Hope and Frustration at U.N. Climate Summit

President Barack Obama addressed world leaders at the United Nations Climate Summit on Tuesday, saying that climate change is a growing threat and the “one issue that will define the contours of this century more dramatically than any other.”

In a nod to the populism of Sunday’s People’s Climate March, where a climate alarm was sounded at 12:58pm, Obama said, "The alarm bells keep ringing. Our citizens keep marching. We cannot pretend we don't hear them. We have to answer the call."

The Climate March drew an estimated 300,000 demonstrators to New York City and hundreds of other climate rallies were held throughout the world on Sunday.

Despite criticism from environmental advocates that his administration has done little for the climate over the past six years, Obama said that the White House has actively addressed the threat from greenhouse gases on global temperatures. Obama cited a working draft on rules to limit carbon emissions from power plants and an executive order, just announced, that instructs federal agencies to acknowledge the climate impact of international development projects.

Many of the nation’s world leaders attended the event; however, China, India and Russia — three of the largest carbon polluters — were not represented by their heads of state. While Russia currently shows little interest in curbing climate change, President Obama assured the assembled leaders he had met with Chinese leaders recently to discuss climate change.

“We have a special responsibility to lead,” Obama said of the U.S. and China. “It's what big nations have to do."

Soon after Obama’s speech, Chinese Vice Premier Zhang Gaoli told the General Assembly that China is committed to significantly reducing its greenhouse-gas emissions. He stated, however, that wealthier developed nations need to act on climate change first, as emerging economies don’t share the historical responsibility for emissions.

Other world leaders vented their frustrations at some developed nations, including the U.S. At issue is the financial commitment to the Green Climate Fund, a $100 billion international endowment for climate mitigation in poorer and developing nations. Gaston Brown, Prime Minister of Antigua and Barbuda, stated that he’s "angry and frustrated" at the lack of commitment by richer nations.

Other speakers included U.N. Secretary General Ban Ki-moon, actor Leonardo DiCaprio and former Vice President Al Gore, all of which urged world leaders to take action.

"Climate change is the defining issue of our age," Ban Ki-moon said in his opening remarks. "It is defining our present. Our response will define our future."

DiCaprio warned the assembled world leaders, “you can make history... or be vilified by it."

"I play fictitious characters often solving fictitious problems," continued the actor. "I believe that mankind has looked at climate change in that same way. As if pretending that climate change wasn't real would somehow make it go away, but I think we all know better than that now."

Ban Ki-moon recently appointed DiCaprio to serve as a "messenger of peace" for the U.N. Ban, Gore and DiCaprio participated in the People’s Climate March on Sunday.

The summit is a kick off to actual negotiations on climate change between nations; none are taking place during the event. It is the precursor to a U.N. Framework Convention for Climate Change, which will take place in Paris, France in December 2015.

Ban hopes the summit gets climate talks back in motion after the eventual failure of the Kyoto Protocol. The United States signed but did not ratify the Protocol and Canada withdrew from it in 2011.

The summit also comes shortly after a intergovernmental report on climate change that says the world has reached the tipping point. According to the report, we may no longer be able to control global warming and associated extreme-weather events unless swift and dramatic action is taken.

Some 120 world leaders, many of them heads of state, attended the summit, the largest number of world leaders ever to attend a conference on climate change. Canada’s Prime Minister Stephen Harper, Australian Prime Minister Tony Abbott, Indian Prime Minister Narendra Modi, Russian President Vladimir Putin, and Chinese President Xi Jinping did not attend. China and India are the world’s two most populous nations and the first- third- and fourth-largest producers of carbon dioxide emissions (the U.S. is second).