United Nations chief Ban Ki-moon singled out sustainable development as the top issue facing the planet and central to this was climate change.
As the world's seven billionth person is expected to be born next month, time was running out, he told a forum at an Australian university on Thursday.
"For that child, and for all of us, we must keep working to fight poverty, create decent jobs, and provide a dignified life while preserving the planet that sustains us.
"That is why the sustainable development agenda is the agenda for the 21st century," he said, AFP reports.
"Above all, that means connecting the dots between challenges such as climate change and water scarcity, energy shortages, global health issues, food insecurity and the empowerment of the world's women."
Ban was speaking at Sydney University in the state of NSW after visiting the Solomon Islands and Kiribati in the Pacific, two small nations he described as "on the front line" of the climate change issue.
"I know, once again, there are the skeptics. Those who say climate change is not real," he said.
"But the facts are clear: global greenhouse gas emissions continue to rise, millions of people are suffering today from climate impacts. Climate change is very real."
He suggested the doubters take a trip to the small Pacific island nation of Kiribati, AFP reports.
"Look into the eyes of the young boy who told me: 'I am afraid to sleep at night' because of the rising water," he said.
"Talk with the parents who told me how they stood guard fearing that their children might drown in their own homes when the tide came in."
Kiribati has indicated it is considering building 'floating islands' to deal with rising sea levels, ABC reports.
President Anote Tong raised the idea on Wednesday on the opening day of a meeting of Pacific leaders in Auckland, New Zealand, Associated Press reports.
Climate change has become a central theme of this year's Pacific Islands Forum thanks to the presence of Ban Ki-moon, who has vowed to put the issue at the forefront of the U.N. agenda.
Ban visited the Solomon Islands and Kiribati before coming to New Zealand and said it only strengthened his view that "something is seriously wrong with our current model of economic development."
The UN holds climate talks in South Africa in November, which are seen as the last chance to renew the five-year Kyoto Protocol, which expires at the end of 2012 and is the only binding global deal to cut greenhouse gases.
"We need ambitious mitigation targets that ensure that any increase in global average temperature remains below two degrees Centigrade," he said.
"Moreover, given that the first commitment period of the Kyoto Protocol expires next year, a political formula must be found to ensure that a robust, post-2012 climate regime is agreed upon, and is not delayed by negotiating gamesmanship."
China and the United States are not bound by the Kyoto Protocol.