United Nations Secretary- General Ban Ki-moon called on Tuesday for "decisive action" to tackle climate change as a global challenge.
"We cannot continue with business as usual," Ban said, addressing an informal debate of the UN General Assembly. "The time has come for decisive action on a global scale."
He said the effects of climate change are already grave, and that they are growing. "We cannot go on this way for long."
"I am convinced that this challenge, and what we do about it, will define us, our era, and ultimately, our global legacy. It is time for new thinking. We all need to shoulder this responsibility, not just for ourselves, but for our children and their children."
Ban said climate change "is just the kind of global challenge that the UN is best suited to address," and a comprehensive agreement is needed to tackle climate change on all fronts, including adaptation, mitigation, clean technologies, deforestation and resource mobilization.
He said a high-level meeting on climate change would be convened in New York at the start of the new General Assembly session next September.
Ban said he has launched a "Greening the UN" initiative, inviting all heads of agencies and other UN bodies to work on a comprehensive plan covering UN premises and operations worldwide.
"Together, we can - and must - take decisive measures this year to address the climate change threat head-on," Ban said.
Tuesday's General Assembly debate featured two interactive panel discussions: "Climate Change: the Science, the Impact and the Adaptation Imperative," and "Mitigation Strategies in the context of Sustainable Development."
On Wednesday, the discussion will be open to all member states, with a focus on national strategies and international commitments to address climate change.
Sheikha Haya Rashed Al Khalifa, president of the General Assembly, said the debate was "a testimony to the political and moral importance of addressing climate change."
"How we protect our environment, manage climate change, secure our planet and safeguard our future, for our children and generations to come, is one of the greatest international challenges of our time," she said.
She said greater investment in climate-friendly energy production and energy efficiency must be made, and technology transfers must be actively pursued to help ensure that all the Millennium Development Goals were met.
"In an interdependent world, we must recognize and champion a multilateral solution to the problems we face," she said. "I believe it is not just more urgent than ever before, but also more possible than before to build a global consensus for tackling environmental change."
The panelists at Tuesday's debate included John Holdren, Harvard University; Nicholas Stern, London School of Economics; Kenrick R. Leslie, Caribbean Community Climate Change Center; and Sunita Narain, director of India's Center for Science and Environment.