Smoke rises from a cement plant in Baokang, in the Hubei province of China. U.S. President Barack Obama is urging world leaders to work together to prepare a new carbon emissions treaty. (Reuters)

U.S. President Barack Obama urged world leaders at a climate-change summit in New York to work together on a new carbon emissions treaty.

"The threat from climate change is serious, it is urgent, and it is growing," Obama said Tuesday. "Our generation's response to this challenge will be judged by history, for if we fail to meet it — boldly, swiftly and together — we risk consigning future generations to an irreversible catastrophe."

U.S. President Barack Obama addresses the UN climate-change summit in New York on Tuesday. (Richard Drew/Associated Press)

World leaders are in New York at the request of UN Secretary General Ban Ki-moon in an attempt to generate political momentum ahead of December's UN Climate Change Conference in Copenhagen, which is meant to create a global treaty on carbon emissions to replace the Kyoto Protocol.

"Failure to reach broad agreement in Copenhagen would be morally inexcusable, economically short-sighted and politically unwise," Ban said as the summit opened. "The science demands it. The world economy needs it."

Prime Minister Stephen Harper was one of about 100 high-profile guests attending the one-day summit to discuss the environment and climate change.

Speaking to reporters, he repeated his call for a new international agreement, adding that Canada will focus on working closely with the U.S.

"I think Canada’s working very closely with the United States, which makes sense, because … we don’t just share an environmental airspace … we’re in an integrated economy," he said.

"So, we think that effective climate-change action has to occur continentally."

'We must all do it together'

Obama urged countries to be ready to move forward in time for the Copenhagen meeting.

"Each of us must do what we can when we can to grow our economies without endangering our planet — and we must all do it together," he said.

France's President Nicolas Sarkozy meets Chinese President Hu Jintao in New York on Monday ahead of a gathering of world leaders to discuss climate change. (Eric Feferberg/Reuters)

Former U.S. president George W. Bush rejected the Kyoto accord based on its exclusion of major developing nations such as China and India.

Developed countries that have damaged the climate over the last century have a responsibility to lead, Obama said.

"But those rapidly growing developing nations that will produce nearly all the growth in global carbon emissions in the decades ahead must do their part as well."

Developing countries must be supported because they do not have the same resources to combat climate change but have the most at stake in a solution, he said.

"It will do little good to alleviate poverty if you can no longer harvest your crops or find drinkable water," Obama said.

Little progress expected

Analysts have said Tuesday's unofficial discussions are not likely to lead to any major progress unless significant plans are laid out by China or the United States.

China and the U.S. each account for about 20 per cent of all the world's greenhouse gas pollution created when coal, natural gas or oil are burned. The European Union is next, generating 14 per cent, followed by Russia and India, which each account for five per cent.

The EU is urging other rich countries to match its pledge to cut emissions by 20 per cent from 1990 levels by 2020, and has said it would cut up to 30 per cent if other rich countries follow suit.

In his opening speech, Obama said the U.S. has entered a "new era" and promoted his country's passing of an energy and climate change bill, investment in renewable energy and efforts to become more energy efficient.

His administration has announced a target of returning to 1990 levels of greenhouse emissions by 2020.

Billions are also being invested in wind energy projects and carbon capture technologies to clean up coal plants, he said.

Push to continue at G20

Obama said he will push G20 members to phase out fossil fuel subsidies when they meet in Pittsburgh on Thursday and Friday.

Meanwhile, China has already said it is seeking to draw 15 per cent of its energy from renewable sources by 2020.

Chinese President Hu Jintao told the summit his nation will continue to take "determined" action.

He laid out new plans for extending China's energy-saving programs and targets for reducing "by a notable margin" the "intensity" of its carbon pollution. He also said China will boost its forest cover and invest in "climate-friendly technologies."

India is also expected to outline plans that include becoming more fuel-efficient, burn coal more cleanly, preserve forests and grow more organic crops.

With files from The Associated Press