UNITED NATIONS, Sept. 23 -- The United Nations wanted the Climate Change Summit "to make history," not just "to talk", the UN Secretary-General Ban Ki-moon said here Tuesday.

"We must set the world on a new course," Ban said when opening the summit. "Climate change is the defining issue of our age. It is defining our present. Our response will define our future."

As the world has never been faced with such a challenge, nor has it encountered such a great opportunity, a low-carbon, climate resilient future will be a better future, which is cleaner, healthier, fairer and more stable, he said.

The UN chief called on all governments to be committed to a meaningful, universal climate agreement in Paris in 2015, and to do their fair share to limit global temperature rise to less than 2 degrees Celsius.

Ban has also called on the summit to catalyze action to reduce emissions, strengthen climate resilience and mobilize political will.

He hoped leaders would utilize what they take from this session to expand commitments at Lima meeting in December in preparation for the Paris conference.

U.S. President Barack Obama said when addressing the opening ceremony that "alarm bells keep ringing, citizens keep marching; We can't pretend we don't hear them."

"We cannot condemn our children, and their children, to a future that is beyond their capacity to repair," he said.

British Prime Minister David Cameron called for support for green growth. "If we get this right, there need not be a trade-off between economic growth and reducing carbon emissions," he said.

"We need to give business the certainty it needs to invest in low carbon," Cameron said. "That means fighting against the economically and environmentally perverse fossil fuel subsidies which distort free markets and rip off taxpayers. It means championing green free trade, slashing tariffs on things like solar panels, and it means giving business the flexibility to pick the right technologies for their needs."

"In short, we need a framework built on green growth, not green tape," he added.

French President Francois Hollande said his country would be contributing 1 billion U.S. dollars to the global Green Climate Fund to help developing nations adapt to the effects of climate change.

Chinese Vice Premier Zhang Gaoli, the special envoy of Chinese President Xi Jinping, said the nation "faces a daunting task of growing the economy, improving people's lives and protecting the environment." China will nonetheless make greater efforts to address climate change more effectively, he added.

"As a responsible major country, China will make a greater effort to more effectively address climate change and take on international responsibilities that are commensurate with its national conditions, stage of development and actual capabilities," he said.

Brazilian President Dilma Rousseff said: "The costs of tackling climate change are high, but the benefits more than outweigh them."

"We must overcome the logic that preventing climate change negatively impacts the economy," she said. "Actions to reduce emissions and to foster adaptation must be considered a source of wealth, as they attract investment and warrant new initiatives of sustainable development."

She rejected the model of developed countries, which is based on high rates of harmful emissions by cutting down forests and damaging the environment.

"We do not want to emulate this model," Rousseff said. "But we will not relinquish the need to reduce inequalities and raise the living standards of our people."

Prime Minister Gaston Browne of Antigua and Barbuda described the effect on countries like those of Small Island Developing State (SIDS).

"We have paid and continue to pay a very high price," he said.

"We, like many another SIDS, contribute the very least to the conditions that cause climate change. We are the victims of the profligacy of others. Therefore there should be no surprise that the people of Antigua and Barbuda like the people of other SIDS are angry and frustrated."

"They are angry that despite all the efforts to develop their economies, despite efforts to build infrastructure to increase productivity to withstand current impacts and to slow uncertain efforts, despite efforts to build foundations of a better life for their children and grandchildren, the devastating effects of climate change destroy their work and set them back year after year, putting our sustainable development pathway off track," Browne said.