Meat and cheese may have to be off the menu if there is to be any hope of hitting climate change targets, a new study suggests.

Cutting greenhouse gas emissions from energy use and transportation is not enough on its own to ensure global temperatures rise by no more than 2C (25.6F), say experts.

The research indicates it will also be necessary to slash emissions from agriculture - which means curbing meat and dairy consumption.

Without such action, nitrous oxide emissions from fields and methane from livestock may double by 2070, it is claimed.

This alone would make meeting the 2C target set by the United Nations impossible.

"We have shown that reducing meat and dairy consumption is key to bringing agricultural climate pollution down to safe levels," said lead scientist Dr Fredrik Hedenus, from Chalmers University of Technology in Sweden.

"Broad dietary change can take a long time. We should already be thinking about how we can make our food more climate friendly."

The call comes despite a rapidly growing demand for meat and dairy foods around the world.

Not only is the world population rising, but more people in developing regions are adopting western lifestyles and diets.

Agricultural emissions are difficult and costly to reduce by means of technology and new production methods, say the researchers writing in the journal Climate Change.

Co-author Dr Stefan Wirsenius, also from Chalmers University of Technology, said: "These emissions can be reduced with efficiency gains in meat and dairy production, as well as with the aid of new technology. But the potential reductions from these measures are fairly limited and will probably not suffice to keep us within the climate limit, if meat and dairy consumption continue to grow."

Livestock add the equivalent of up to 7.1 gigatonnes of carbon dioxide to the atmosphere each year - or 14.5% of all human-caused greenhouse gas emissions, according to a United Nations report published last year.

Beef and lamb are said to account for the most emissions relative to the energy they provide.

By 2050, estimates indicate that beef and lamb production will make up half of all agricultural greenhouse gas emissions, while only contributing 3% of human calorie intake.

Cheese and other dairy products are expected to generate about a quarter of total agricultural climate pollution in the next 40 years.

The research is reported on the eve of the latest assessment of global warming impacts from the Intergovernmental Panel on Climate Change (IPCC) to be presented tomorrow.