The global climate
What does our diet have to do with climate change?
The atmosphere, the gaseous envelope surrounding the earth, makes life on our planet possible. Its composition is significantly influenced by life itself and has changed dramatically throughout various geological eras. Water vapour and trace gases, such as carbon dioxide, methane, and nitrous oxide, trap part of the energy radiating onto the earth, causing the surface to absorb more heat than it releases. This natural greenhouse effect is what allows life as we know it to exist. Without it, the average global temperature would be -18°C instead of +15°C..
When humans cause the release of more greenhouse gases (particularly CO₂) into the atmosphere than natural processes can absorb, we increase the earth’s temperature. But how do we manage to release this level of greenhouse gas emissions in the first place? To answer this, we must look at the carbon present in all living organisms, which combines with oxygen to form CO₂ in the atmosphere. During photosynthesis, plants absorb CO₂ using solar energy and release oxygen. The CO₂, combined with water, is converted into sugars that form leaves, stems, roots, and other organic matter. This photosynthesis nourishes animals, fungi, microorganisms, and humans.
Thus, plants remove carbon from the atmosphere. Some of it returns to the cycle when microorganisms break down plant matter into CO₂, or when wood burns. Another portion is permanently stored in soil and on the seabed.
For thousands of years, the carbon cycle remained relatively stable, until about 200 years ago when humans began extracting and burning increasing amounts of fossil fuels, i.e. carbon stored in the earth as oil, coal, and natural gas. Simultaneously, we are reducing the carbon storage in soils by converting forests, wetlands, and meadows into farmland, settlements, and deserts.
Nearly 40 percent of all additional greenhouse gases emitted by humans are directly or indirectly linked to food and agricultural production. These emissions come from deforestation, chemicals, mechanisation, cultivation, transportation, cooling, heating, packaging and food waste. Agriculture also significantly contributes to the emission of high-impact greenhouse gases like methane (from livestock fermentation and wet-rice fields) and nitrous oxide (from fertilisers). To achieve the Climate Convention’s goal of limiting global warming to 1.5°C, we must reduce these emissions by almost 90 percent by 2050.
From the field to the plate and ultimately to waste, different foods vary starkly in the level of emissions they are responsible for. Since one calorie of animal product requires significantly more plant calories to produce it, and methane is also emitted in the process, meat and dairy products have a particularly high greenhouse gas footprint. Meat and milk from cows grazing on local pastures are more climate-friendly than those from animals fed soy imported from Brazil. A strawberry flown halfway around the world is a far bigger contributor to climate change than a locally grown one- unless it comes from an oil-heated greenhouse. The energy used for freezing and heating during processing also plays a critical role in determining the extent of the detrimental impact on the climate.
