Could we meet the Paris goals if everyone went vegan?

Not by diet alone, but the research suggests the goal can hardly be met without changing food. A vegan world would help in three ways.

First, emissions fall. The food system causes 31 percent of the world's emissions1, and animal foods, including their feed, cause 58 percent of food emissions2. A study in Science finds that even if all fossil fuel emissions stopped at once, current trends in the food system would put the 1.5 degree target out of reach and threaten the 2 degree target by the end of the century3.

Second, land is freed. The IPCC describes a scenario where nobody eats animal products: by 2050 the world could feed itself on less land than today, forests could grow back, and emissions from farming and land would fall to a third, 7.8 Gt CO2e less per year4. Another study estimates that a global shift to plant-based diets by 2050 could let nature take up 332 to 547 Gt of CO2. That equals 99 to 163 percent of the CO2 budget that gives a 66 percent chance of keeping warming below 1.5 degrees5. The carbon is taken up over decades, though, as forests and other nature grow back.

Third, less methane works fast. Methane leaves the atmosphere quickly, so lower emissions show results within about a decade6. The UN Environment Programme writes that the Paris Agreement can only succeed if methane is cut on top of CO27.

Diet cannot do it alone, however. The same Science study concludes that 1.5 degrees requires rapid and ambitious changes both in the food system and in every other sector3. Fossil fuels must still be phased out.