Meat is a wasteful use of water and creates a lot of greenhouse gases. It puts enormous pressure on the world’s resources. A vegetarian diet is bette… - Nicholas Stern, Baron Stern of Brentford

If we do not cut emissions, we face even more devastating consequences, as unchecked they could raise global average temperature to 4C or more above pre-industrial levels by the end of the century. The shift to such a world could cause mass migrations of hundreds of millions of people away from the worst-affected areas. That would lead to conflict and war, not peace and prosperity. … We also underestimated the potential importance of strong feedbacks, such as the thawing of the permafrost to release methane, a powerful greenhouse gas, as well as tipping points beyond which some changes in the climate may become effectively irreversible.

We should remember that the last time global temperature was 5C different from today, the Earth was gripped by an ice age. So the risks are immense and can only be sensibly managed by reducing greenhouse gas emissions, which will require a new low-carbon industrial revolution.