4.1 What would be a safe upper limit to GHG emissions and where might reductions come from?

4.1.1 Significant global GHG emissions reductions are required across all sectors.

IPCC reports identify likely outcomes for different global temperature increases resulting from current GHG emission trajectories. A common assumption is that an acceptable global warming limit is a 2°C rise in average global temperature above pre-industrial levels, although this is subject to debate and uncertainty.

The 2015 climate summit (COP21) in Paris resulted in reaffirmation by nations that the goal of 2°C remains, but with a strong signal of intent to limit the temperature increase to 1.5°C in response to calls by vulnerable states (specifically low-lying island nations).

The recent IPCC report calculates that GHG emissions reductions of between 40% and 70%, by 2050, will be needed for the 2°C scenario to likely be achieved. Reducing emissions to zero by 2100 is likely needed to maintain temperatures within this limit.

The IPCC report calculates that in order to likely stay within the 1.5°C limit, GHG emissions will need to be reduced by 70-95% by 2050.

Reductions of 70–95% in global GHG emissions across all sectors of human activity could be needed by 2050

This is considered to be a significant technical and socio-economic challenge.

4.1.2 The food system needs to play its part.

Food-related GHGs are estimated to contribute around 20-30% of total global emissions (see Chapter 3).

Under the 2°C scenario (entailing emissions reductions of at least 40-70%), current food-related emissions could potentially make up 100% of the total ‘allowable’ budget for emissions.

Under the 1.5°C scenario (entailing emissions reductions of at least 70-95%), current food-related emissions would far exceed the total budget for emissions.

These ambitious reduction targets mean that food systems cannot be excluded from emissions reduction strategies

Vermeulen, Campbell and Ingram (2012).

While there is high uncertainty concerning actual safe limits, these figures do make it clear that GHG emissions from food systems need to be addressed. The level of absolute reductions required from the food sector is difficult to quantify, however, because the answer also depends on emission reductions in other sectors; the more that can be done to reduce emissions from the transport or built environment sectors (for example) the less needs to be done in the food sector, and vice versa. However, major reductions in all sectors will almost certainly be needed. It is also unclear what the best approaches for reductions in food-related emissions are (see later in this chapter), but the message is clear: food systems need to be part of the solution.

4.1.3 But food-related GHGs are likely to increase.

Projections suggest that demand for food will continue to grow

Demand for food is projected to rise by 60% by 2050. But these are based on current trajectories, and are not definite outcomes.


As Chapter 1 shows, demand for food is anticipated to increase by 60% by 2050. This is based on assumptions that:

  • The global population will continue to rise by another 2 billion people.
  • Poorer countries are expected to move out of poverty, leading to rising incomes in these countries.
  • Higher incomes lead to increased spending on resource-intensive foods, including animal products.
  • Increased demand for meat will result in an increased demand for arable crops as feed inputs.

However, these are projections based on the above assumptions, historical trends and current trajectories. The extent to which they come true will depend on global economic development, the actions of governments, citizens and industry stakeholders.

Issues around changes in eating habits and sustainable eating diets are discussed in Chapter 9 and Chapter 10.