One of the world's leading climate change gurus urged people to become vegetarian today, to help beat global warming.
Nicholas Stern, the author of an influential 2006 review of climate change, said methane emissions from cows and pigs were putting "enormous pressure" on the world and people needed to think about what they ate.
He told The Times: "Meat is a wasteful use of water and creates a lot of greenhouse gases. It put enormous pressure on the world's resources. A vegetarian diet is better."
The former World Bank chief economist was speaking ahead of the climate change conference in Copenhagen this December, which is expected to be attended by thousands of delegates from around the world.
Lord Stern said a successful conference would result in higher costs for meat and other foods that generate large quantities of greenhouse gases.
He also compared his stance on meat to the change in attitudes to drink-driving.
"I think it's important that people think about what they are doing and that includes what they are eating," the London School of Economics professor said.
"I am 61 now and attitudes towards drinking and driving have changed radically since I was a student.
"People change their notion of what is responsible. They will increasingly ask about the carbon content of their food."
Methane is 23 times more powerful than carbon dioxide as a greenhouse gas, and it has been estimated that livestock accounts for a fifth of the global warming impact.
In his interview with The Times, Lord Stern said if business continued as usual then temperatures could increase by 5C by early next century.
"These kinds of changes will have huge consequences - southern Europe is likely to be a desert; hundreds of millions of people will have to move. There will be severe global conflict."
His 2006 review warned that if the world did not act on global warming, the cost would be at least 5 per cent of GDP "now and forever".
"Climate change is a serious global threat, and it demands an urgent global response," he said.