In 2010, as many as 50 million could be displaced due to climate change, desertification and deforestation, said Yve de Boer, executive Secretary of the United Nations Framework Convention on Climate Change (UNFCCC) at the opening session for a high-level segment of the UN climate change conference in Bali, a resort island of Indonesia.

"Competing for war, energy and food can lead to ethnic rivalry and regional conflicts," he said.

He said, "To meet the drastic increase in the world's hunger for energy, a massive investment of US$20 trillion is needed up to 2030. More than half of these investments are required in developing countries, where energy is needed for economic growth."

He warned global emissions of greenhouse gases will increase by 50 percent in 2050 instead of decreasing by 50 percent, if the international community does not succeed in changing the course of this investment super tanker into a low-emissions direction.

Citing reports from the UN Nobel-prize winning Intergovernmental Panel on Climate Change (IPCC), he said by 2020, between 75 million and 250 million people in Africa are projected to be exposed to increased water stress due to climate change.

By the 2050s, freshwater availability for millions in Asia will be threatened, because glaciers that provide drinking water are melting, he added.

One-tenth of the global population lives in coastal areas that lie within just 10 meters above sea level and are exposed to seaward hazards such as flooding, storms and cyclones.

"We have come together at this (Bali) conference at the cusp of an incredible year for climate change. The heyday of the climate skeptic has been put to rest once and for all, and political momentum and global public awareness for climate change have never been higher," he said.

The Dec. 3-14 UN climate conference is tasked with drawing a roadmap for negotiation on a new climate deal before the current phase of the Kyoto Protocol expires in 2012.