UN Secretary General Ban Ki-moon said that global warming posed the same threat to humanity as war and warned of an "unconscionable legacy" being left for future generations.

In a speech to a UN International School Conference, Ban acknowledged that the "majority" of the UN's work still focuses on the prevention and resolution of conflict.

"But the danger posed by war to all of humanity -- and to our planet -- is at least matched by the climate crisis and global warming," he said.

Pledging to raise the issue at a summit of the G8 major industrialised nations in June, Ban said the absence of decisive measures to combat climate change would place an appalling burden on succeeding generations.

"That would be an unconscionable legacy; one which we must all join hands to avert," he said. "As it stands, the damage already inflicted on our ecosystem will take decades, perhaps centuries, to reverse -- if we act now."

The secretary general highlighted the far-reaching ramifications of global warming and its impact on economic growth, the spread of disease, migration patterns and other changes that "are likely to become a major driver of war and conflict."

Referring to the G8 summit in Germany, Ban stressed that the task of tackling climate change was beyond the capacity of any one nation.

"We are all complicit in the process of global warming ... these issues transcend borders," he said. "Only concerted and coordinated international action, supported and sustained by individual initiative, will be sufficient."

The United Nations is due to hold a conference on climate change in Bali in December.

Earlier this month, UN scientists delivered their starkest warning yet about global warming, saying fossil fuel pollution would raise temperatures this century, worsen floods, droughts and hurricanes, melt polar sea ice and damage the climate system for a thousand years to come.

In its first assessment in six years, the Intergovernmental Panel on Climate Change (IPCC) dealt a crippling blow to the shrinking body of opinion that claims higher temperatures in past decades have been driven by natural, not man-made, causes.

The United Nations' paramount scientific authority on global warming highlighted a range of changes that had taken place in Earth's ice cover, rainfall patterns and permafrost and declared that most of the temperature rise over the past 50 years had "very likely" been caused by human activity.