Global meat consumption needs to be cut to ensure the world avoids "dangerous" climate change, a report has warned.
A worldwide shift towards lower-meat diets, which would also be healthier for people, would help close the gap between emissions cuts pledged by countries and what is needed to curb temperature rises to prevent the worst impacts of global warming, it said.
The report from Chatham House recommends governments take action to curb meat consumption, which could include making meat more expensive through a carbon tax and using procurement for schools and hospitals to push healthier diets.
The livestock sector accounts for 15% of global greenhouse emissions, caused by growing crops for feed, converting forests and other land for growing animal feed, gas and manure from the animals, heating and powering buildings and transporting meat products.
As well as causing the same level of greenhouse gases as the tailpipe emissions of all the vehicles in the world, increasing meat consumption is bad for people's health, linked to cancer, heart disease, obesity and spread of antibiotic-resistant disease.
The report, released ahead of key UN talks on tackling climate change, warns that pledges made by countries ahead of the talks in Paris on the action they will take to cut emissions put the world on track for around 3C of warming by 2100.
Changing diets to ensure healthy levels of meat consumption could deliver 25% of the remaining emissions reductions needed to put the world on a path to curb temperature rises to 2C above pre-industrial levels, it said.
Countries have pledged to keep temperature rises from going beyond 2C, as a threshold beyond which the worst impacts of climate change are expected.
Meat consumption per person is already above healthy levels worldwide and set to increase by 76% by 2050, the report said.
People in developed countries eat double what is considered healthy, and people in developing countries are eating more as incomes increase.
Report author Laura Wellesley said: "Reducing meat consumption is a real win-win for health and the climate.
"As governments look for strategies to close the Paris emissions gap quickly and cheaply, dietary change should be high on the list."
The report said governments were ignoring the opportunity to cut emissions from meat in the face of fears that interfering with lifestyle choices will provoke a public backlash.
But research for the study suggests that once people are aware of the climate and health impacts of eating too much meat, though it may not influence their personal choices very much, they are more accepting of the need for government action - even unpopular interventions such as putting up prices.
Strategies to curb meat consumption could also include ensuring people have more choice in food outlets, promoting healthy eating and support innovation into alternatives to meat.
Ms Wellesley added: "Raising awareness about the health and environmental impacts of meat is an important first step but on its own it will not lead to significant behaviour change.
"Governments must do more to influence diets."