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If climate change sparks a global collapse this century, future historians are unlikely to acknowledge what caused it, says Norwegian scholar Jorgen Randers.

Delivering the 2006 Templeton Lecture at Sydney University last night, Professor Randers said that when future generations look back over the century, they are unlikely to recognise climate change as the root cause of a resource-induced global collapse.

"Instead, historians will describe a collapse as caused by large scale mismanagement. The Iraq War is a case in point. Who will say it's about scare oil? A climate change global collapse could remain fiction, even if it proved to be fact," argued Professor Randers.

Professor Randers, from the Norwegian School of Management, co-authored the prophetic 1972 book The Limits to Growth that first introduced the concept of global collapse as "a sudden and uncontrollable decline in human welfare". It argued that unless proper counter action was taken, planetary limitations could induce a collapse in the first half of the 21st century.

Professor Randers's definition of a resource-induced collapse would involve a billion people losing at least 50 per cent of what they value within 25 years.

"Since my 1972 book was published, we have not seen a global collapse, but there have been several small ones," he said. The North Atlantic cod fisheries have collapsed, the last tree on Easter Island has been cut down, and the global economy has suffered stock market crashes in 1990 and 2000, he explained.

It is unlikely that oil scarcity will prove capable of triggering a global collapse, according to Professor Randers. "The period of high oil prices will give strong stimulus for increased energy efficiency," he said.

However, the rapid increase in emissions of climate gases does have the potential to cause a collapse. This is because gases emitted decades ago will cause damage for another century or more, he explained.

Secondly, it is because "there are self-reinforcing effects of climate gas emissions." As the polar ice-caps melt, for example, the dark ocean absorbs even more solar energy, heating up the atmosphere and increasing the melting rate of the ice.

Professor Randers ended by calling for strong government leadership on climate change, saying that change is "highly do-able and not terribly expensive".