"In the future you will find transport vehicles not being run on internal combustion engines or diesel engines, but being run by fuel cells," he said.

"In the next 50 years you will find a radical change in the way we use energy," he said.

The shift will hurt oil firms, who have opposed the Kyoto Protocol, a global pact to cut most industrial nations' net emission of greenhouse gases such as carbon dioxide.

Environmentalists have alleged Pachauri's election was a result of active lobbying by the United States, which refused to join the Kyoto Protocol and wanted to oust Robert Watson, a less acceptable candidate. Pachauri denies the allegation.

Pachauri said the move away from conventional sources of energy such as coal and oil was gaining momentum.

"I think things are changing very rapidly. If you look at wind energy, there have been remarkable technological improvements in wind machines."

"I think it's bound to accelerate. It's bound to expand... Globally we will have to move to lower carbon intensity fuels. There is no getting away from that."

Scientific opinion is still split on the degree to which carbon dioxide and other greenhouse gases in the atmosphere are behind global warming.

In theory, greenhouse gases trap heat from the sun and warm the planet. They are pumped into the atmosphere by human activity, burning fossil fuels such as coal, oil and gas. Carbon dioxide is also produced by natural sources.

Pachauri said oil would continue to be important but technological advances would keep prices in check as higher oil prices would encourage the use of alternative fuels and depress prices by reducing petroleum demand.

"So oil, of course, will have a future but it will probably have a declining future."

He said some "enlightened" oil companies had a sense of social responsibility and saw a business opportunity in renewable sources of energy. "There are others...who I believe are not moving at all."

Oil companies have been concerned about the activities of the IPCC, and Pachauri is not surprised.