Greenhouse gases such as carbon dioxide, methane and nitrous oxide trap heat in the atmosphere. Burning fossil fuels, farming and clearing forests have pushed their levels higher than at any time in at least 800,000 years. According to the IPCC, this has warmed the planet by about 1.1°C, causing hotter extremes, rising seas and ecosystem loss.
Greenhouse gases are gases that absorb heat radiated from the Earth's surface and slow its escape to space. The main ones are carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) and fluorinated gases (F-gases).
They make up a tiny fraction of the air, but they control how much heat the planet keeps. Without any of them, Earth would be too cold for most life. With too much of them, it warms.
Sunlight warms the Earth's surface, and the surface gives off heat. Greenhouse gases absorb some of that heat and send part of it back down, which keeps the lower atmosphere warmer than it would otherwise be.
This natural greenhouse effect is what makes the planet habitable. The problem is the extra gas people have added since the 1800s. More gas means more heat is held back, and the average temperature rises until the planet reaches a new balance.
CO2 causes most of the warming because there is so much of it and it lasts for centuries. Methane and nitrous oxide are emitted in smaller amounts but trap far more heat per tonne. F-gases are emitted in tiny amounts but are thousands of times stronger than CO2.
| Gas | Share of 2024 global emissions (EDGAR) | Warming per tonne vs CO2 (GWP100, IPCC AR6) | Main human sources | How long it lasts |
| Carbon dioxide (CO2) | ~74.5% (fossil CO2) | 1 | Coal, oil and gas; cement; deforestation | Centuries to millennia |
| Methane (CH4) | ~17.9% | 27.0 (non-fossil) to 29.8 (fossil) | Livestock, rice, landfill, oil and gas leaks, coal mines | About 12 years |
| Nitrous oxide (N2O) | ~4.8% | 273 | Fertiliser, manure, some chemical production | About 110 years |
| F-gases (HFCs, PFCs, SF6, NF3) | ~2.8% | Hundreds to over 20,000 | Refrigeration, air conditioning, electrical equipment, electronics | Years to thousands of years |
Sources: EDGAR 2025 report (JRC, September 2025; shares of 53.2 GtCO2e in 2024, excluding land use); IPCC AR6 WGI (2021) for GWPs and lifetimes.
To compare these gases, companies convert them into one unit, carbon dioxide equivalent. See CO2e: definition, calculation and examples.
CO2 comes mainly from burning coal, oil and gas for power, heat, industry and transport, and from cement making and deforestation. The IPCC reports that atmospheric CO2 reached 410 parts per million in 2019, higher than at any time in at least two million years (IPCC AR6 WGI, 2021).
Methane traps much more heat than CO2 but breaks down in about a decade, so cutting it slows warming quickly. The UN Environment Programme estimates that about 40% of human methane emissions come from agriculture, about 35% from fossil fuels and about 20% from waste (Global Methane Assessment, UNEP and CCAC, 2021). In 2019 methane concentrations were 1,866 parts per billion, about two and a half times pre-industrial levels (IPCC AR6 WGI).
Nitrous oxide comes mostly from nitrogen fertiliser and manure, with some from making nitric and adipic acid. It lasts more than a century, so emissions build up. For food and agriculture companies, it is often a large part of the farm-level footprint. See agricultural greenhouse gas emissions.
F-gases are made by industry, mostly for cooling, insulation and electrical equipment. Small leaks matter because of how strong they are. Sulphur hexafluoride has a 100-year GWP of 25,200 (IPCC AR6).
Global greenhouse gas emissions reached a record 57.7 GtCO2e in 2024, up 2.3% on 2023, according to UNEP's Emissions Gap Report 2025. That figure includes land-use change. Fossil fuel use and deforestation drove most of the increase.
The IPCC concludes that it is "unequivocal that human influence has warmed the atmosphere, ocean and land" (IPCC AR6 WGI Summary for Policymakers, 2021).
More greenhouse gas has raised global temperatures, and that sets off other changes: heavier rainfall and drought, more intense heatwaves, melting ice, rising seas and stress on ecosystems.
| Effect | What the evidence shows | Source |
| Rising temperatures | Global surface temperature was about 1.1°C higher in 2011–2020 than in 1850–1900 | IPCC AR6 WGI (2021) |
| Record recent years | 2024 was about 1.55°C above pre-industrial, the first calendar year above 1.5°C. 2015–2025 are the eleven warmest years on record | WMO (November 2025) |
| Sea level rise | Global mean sea level rose about 0.20 m between 1901 and 2018, and the rate is speeding up | IPCC AR6 WGI (2021) |
| Extreme weather | Human influence has made heatwaves more frequent and intense, and has increased heavy rainfall in many regions | IPCC AR6 WGI (2021) |
| Biodiversity loss | Warming is shifting where species can live and has caused local losses of species | IPCC AR6 WGII (2022) |
A single year above 1.5°C does not mean the Paris Agreement limit has been passed. That limit refers to long-term averages over about 20 years.
For most companies, climate change shows up in two ways: physical risk to operations and supply chains, and transition pressure from regulators, investors and customers to cut emissions.
On-farm emissions from feed, livestock and fertiliser are often the hardest part of a food company's footprint to see. Working with Terrascope, Greenfields found that its cattle feed emissions could fall by more than 50%.
Terrascope measures every greenhouse gas in your footprint, not just CO2, and shows which sources and suppliers drive it.
For the full method, read our main guide on how to calculate GHG emissions. To see which gases drive your own footprint, talk to our team.
The main greenhouse gases are carbon dioxide, methane, nitrous oxide and fluorinated gases (HFCs, PFCs, SF6 and NF3). Water vapour also traps heat, but its amount depends on temperature, so it amplifies warming rather than driving it.
Carbon dioxide causes the most warming overall, because so much is emitted and it stays in the air for centuries. Per tonne, methane, nitrous oxide and F-gases are far stronger, which is why companies convert all gases into CO2e.
They absorb heat given off by the Earth's surface and send part of it back down. Human activity has added more of these gases, so more heat is held in the climate system. That raises average temperatures and changes rainfall, ice cover and sea levels.
Energy is the biggest source. Burning coal, oil and gas for electricity, heat, industry and transport produces most global emissions. Agriculture, forestry and land use come next. See our post on which sector emits the most.
No. The natural greenhouse effect keeps Earth warm enough for life. The problem is the extra greenhouse gas from human activity, which strengthens the effect and warms the planet.
The Paris Agreement (2015) is a UN treaty to hold warming well below 2°C above pre-industrial levels and pursue efforts to limit it to 1.5°C. Countries set national targets, called Nationally Determined Contributions, and report on their progress.