The authors of this paper calculate the carbon footprint of various recommended healthy diets around the world and find that most recommendations are inconsistent with the 1.5°C climate target, and are probably also inconsistent with the 2.0°C target unless non-food sectors almost completely cut their carbon emissions by 2050. Annual per capita diet-related carbon footprints vary from 687 kg CO2 eq. for Indian vegetarian dietary guidelines to 1579 kg CO2 eq. for US dietary guidelines.
The figure below shows the carbon footprints of each recommended diet. Note that these are not the same as the actual consumption patterns of populations in those countries. See for example the paper Evaluating the environmental impacts of dietary recommendations, which finds that in high-income and upper-middle-income countries, actual dietary emissions are higher than they would be if people followed the nationally recommended diets, but in poorer middle-income countries, actual dietary emissions are lower than if people followed the nationally recommended diets.
Below, the two rightmost columns, showing the per capita annual carbon budget for the 1.5°C and 2.0°C climate targets, represent emissions from all sectors, not just food. This means that in most cases, a nationally recommended diet alone would cause emissions exceeding the individual limit consistent with the 1.5°C climate target, and that recommended diets generally take up one half to two-thirds of the personal emissions limit consistent with the 2.0°C target.
The global food system faces an ambitious challenge in meeting nutritional demands whilst reducing sector greenhouse gas emissions. These challenges exemplify dietary inequalities—an issue countries have committed to ending in accord with the Sustainable Development Goals (by 2030). Achieving this will require a convergence of global diets towards healthy, sustainable guidelines. Here we have assessed the implications of dietary guidelines (the World Health Organization, USA, Australian, Canadian, German Chinese and Indian recommendations) on global greenhouse gas emissions. Our results show a wide disparity in the emissions intensity of recommended healthy diets, ranging from 687 kg of carbon dioxide equivalents (CO2e) capita−1 yr−1 for the guideline Indian diet to the 1579 kg CO2e capita−1 yr−1 in the USA. Most of this variability is introduced in recommended dairy intake. Global convergence towards the recommended USA or Australian diet would result in increased greenhouse gas emissions relative to the average business-as-usual diet in 2050. The majority of current national guidelines are highly inconsistent with a 1.5 °C target, and incompatible with a 2 °C budget unless other sectors reach almost total decarbonisation by 2050. Effective decarbonisation will require a major shift in not only dietary preferences, but also a reframing of the recommendations which underpin this transition.
Ritchie, H., Reay, D.S. and Higgins, P., 2018. The impact of global dietary guidelines on climate change. Global Environmental Change, 49, pp.46-55.
View the full paper here. See also the Foodsource resource Which diets generate fewer GHG emissions and other environmental impacts?