Even having one meat-free day a week will help cut greenhouse-gas emissions and other environmental problems -- including habitat destruction -- associated with rearing cattle and other livestock, Rajendra Pachauri, chairman of the U.N. Intergovernmental Panel on Climate Change, told The Observer of London.

"In terms of immediacy of action and the feasibility of bringing about reductions in a short period of time, it clearly is the most attractive opportunity," said Pachauri, a vegetarian who shared the Nobel Peace Prize on behalf of the U.N. panel with former U.S. Vice President Al Gore last December. "Give up meat for one day (a week) initially, and decrease it from there."

The Observer called it the most controversial advice yet provided by the panel on how individuals could tackle global warning.

The United Nations Food and Agriculture Organization, meanwhile, estimates meat production accounts for nearly one-fifth of global greenhouse-gas emissions.

These are generated in animal-feed production -- but also because cows emit methane gas, which contributes to global warming 23 times more than carbon dioxide, the U.N. agency said.

The agency has also forecast meat consumption will double by mid-century.