Greenhouse gas emissions (GHG emissions) from human activities intensify the greenhouse effect which contributes to climate change. Carbon dioxide () from burning fossil fuels (such as coal, oil, and natural gas) is the main cause of climate change. The largest annual emissions are from China followed by the United States, which has higher emissions per capita. The main producers fueling the emissions globally are large oil and gas companies. Emissions from human activities have increased atmospheric carbon dioxide by about 50% over pre-industrial levels. The growing levels of emissions have varied, but have been consistent among all greenhouse gases. Over 60 billion tons were emitted in 2025, higher than any year before. Total cumulative emissions from 1870 to 2022 were 703 (2575 ), of which 484±20 (1773±73 ) from fossil fuels and industry, and 219±60 (802±220 ) from land use change. Land-use change, such as deforestation, caused about 31% of cumulative emissions over 1870–2022, coal 32%, oil 24%, and gas 10%.
Carbon dioxide is the main greenhouse gas resulting from human activities. It accounts for more than half of warming. Methane (CH4) emissions have almost the same short-term impact. Nitrous oxide (N2O) and fluorinated gases (F-gases) play a lesser role in comparison. Emissions of carbon dioxide, methane and nitrous oxide in 2023 were all higher than ever before.
Electricity generation, heat and transport are major emitters; overall energy is responsible for around 73% of emissions. A growing concern for electricity usage is the expansion of artificial intelligence (AI), which is projected to significantly increase global energy demand. Deforestation and other changes in land use also emit carbon dioxide and methane. The largest source of anthropogenic methane emissions is agriculture, closely followed by gas venting and fugitive emissions from the fossil-fuel industry. The largest agricultural methane source is livestock. Agricultural soils emit nitrous oxide partly due to fertilizers. Similarly, fluorinated gases from refrigerants play an outsized role in total human emissions.
The current -equivalent emission rates, averaging 4.9 tonnes per person per year, are well over twice the estimated rate of 2.3 tons required to stay within the 2030 Paris Agreement increase of 1.5 °C (2.7 °F) over pre-industrial levels. Annual per capita emissions in the industrialized countries are typically as much as ten times the average in developing countries.
The carbon footprint (or greenhouse gas footprint) serves as an indicator to compare the amount of greenhouse gases emitted over the entire life cycle from the production of a good or service along the supply chain to its final consumption.IPCC, 2022: Annex I: Glossary [van Diemen, R., J.B.R. Matthews, V. Möller, J.S. Fuglestvedt, V. Masson-Delmotte, C. Méndez, A. Reisinger, S. Semenov (eds)]. In IPCC, 2022: Climate Change 2022: Mitigation of Climate Change. Contribution of Working Group III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [P.R. Shukla, J. Skea, R. Slade, A. Al Khourdajie, R. van Diemen, D. McCollum, M. Pathak, S. Some, P. Vyas, R. Fradera, M. Belkacemi, A. Hasija, G. Lisboa, S. Luz, J. Malley, (eds.)]. Cambridge University Press, Cambridge, UK and New York, NY, USA. doi: 10.1017/9781009157926.020 Carbon accounting (or greenhouse gas accounting) is a framework of methods to measure and track how much greenhouse gas an organization emits. This accounting is used to help understand the various effects of emissions on positive and negative impacts they have on the climate including on human mortality.
Relevance for greenhouse effect and global warming
Overview of main sources
Relevant greenhouse gases
The major anthropogenic (human origin) sources of greenhouse gases are carbon dioxide (), nitrous oxide (), methane and three groups of fluorinated gases (sulfur hexafluoride (), hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs, sulphur hexafluoride (SF6), and nitrogen trifluoride (NF3)).Dhakal, S., J.C. Minx, F.L. Toth, A. Abdel-Aziz, M.J. Figueroa Meza, K. Hubacek, I.G.C. Jonckheere, Yong-Gun Kim, G.F. Nemet, S. Pachauri, X.C. Tan, T. Wiedmann, 2022: Chapter 2: Emissions Trends and Drivers. In IPCC, 2022: Climate Change 2022: Mitigation of Climate Change. Contribution of Working Group III to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [P.R. Shukla, J. Skea, R. Slade, A. Al Khourdajie, R. van Diemen, D. McCollum, M. Pathak, S. Some, P. Vyas, R. Fradera, M. Belkacemi, A. Hasija, G. Lisboa, S. Luz, J. Malley, (eds.)]. Cambridge University Press, Cambridge, UK and New York, NY, USA. doi: 10.1017/9781009157926.004 Though the greenhouse effect is heavily driven by water vapor, human emissions of water vapor are not a significant contributor to warming.
Although CFCs are greenhouse gases, they are regulated by the Montreal Protocol which was motivated by CFCs' contribution to ozone depletion rather than by their contribution to global warming. Ozone depletion has only a minor role in greenhouse warming, though the two processes are sometimes confused in the media. In 2016, negotiators from over 170 nations meeting at the summit of the United Nations Environment Programme reached a legally binding accord to phase out hydrofluorocarbons (HFCs) in the Kigali Amendment to the Montreal Protocol. The use of CFC-12 (except some essential uses) has been phased out due to its ozone depleting properties. The phasing-out of less active HCFC-compounds will be completed in 2030.Montreal Protocol
Human activities
Starting about 1750, industrial activity powered by fossil fuels began to significantly increase the concentration of carbon dioxide and other greenhouse gases. Emissions have grown rapidly since about 1950 with ongoing expansions in global population and economic activity following World War II. As of 2021, measured atmospheric concentrations of carbon dioxide were almost 50% higher than pre-industrial levels.
The main sources of greenhouse gases due to human activity (also called carbon sources) are: Burning fossil fuels: Burning oil, coal and gas is estimated to have emitted 37.4 billion tonnes of -eq in 2023. The largest single source is coal-fired power stations, with 20% of greenhouse gases (GHG) as of 2021. Land use change (mainly deforestation in the tropics) accounts for about a quarter of total anthropogenic GHG emissions. Livestock enteric fermentation and manure management, paddy rice farming, land use and wetland changes, human-made lakes, pipeline losses, and covered vented landfill emissions leading to higher methane atmospheric concentrations. Many of the newer style fully vented septic systems that enhance and target the fermentation process also are sources of atmospheric methane. Use of chlorofluorocarbons (CFCs) in refrigeration systems, and use of CFCs and halons in fire suppression systems and manufacturing processes. Agricultural soils emit nitrous oxide (N2O) partly due to application of fertilizers. The largest source of anthropogenic methane emissions is agriculture, closely followed by gas venting and fugitive emissions from the fossil-fuel industry. The largest agricultural methane source is livestock. Cattle (raised for both beef and milk, as well as for inedible outputs like manure and draft power) are the animal species responsible for the most emissions, representing about 65% of the livestock sector's emissions.
Global estimates
Global greenhouse gas emissions are about 50 Gt per year, and for 2024 have been estimated at 57.7 Gt eq. The largest contributor of total GHG emissions came from the power sector at approximately 27%, followed by transport at 15%, while industrial energy and agriculture each contributed 11%.
The current -equivalent emission rates averaging 4.9 tonnes per person per year, are over twice the estimated rate 2.3 tons required to stay within the 2030 Paris Agreement increase of 1.5 °C (2.7 °F) over pre-industrial levels.
While cities are sometimes considered to be disproportionate contributors to emissions, per-capita emissions tend to be lower for cities than the averages in their countries.
A 2017 survey of corporations responsible for global emissions found that 100 companies were responsible for 71% of global direct and indirect emissions, and that state-owned companies were responsible for 59% of their emissions.
China is, by a significant margin, Asia's and the world's largest emitter; it emits around 10 billion tonnes each year, more than one-quarter of global emissions. Other countries with fast growing emissions are United States, India, Russia, and Indonesia. Among these top emitters, in 2024, China, India, Russia and Indonesia increased their emissions compared to 2023, with Indonesia having the largest increase in relative terms, and India the largest absolute increase by 164.8 Mt CO2eq. Conversely, EU-27 GHG emissions, excluding LULUCF, were approximately 35% lower than in 1990 reaching 3.2 Gt CO2eq.
2015 was the first year to see both total global economic growth and a reduction of carbon emissions.
High income countries compared to low income countries
Annual per capita emissions in the industrialized countries are typically as much as ten times the average in developing countries. Due to China's fast economic development, its annual per capita emissions are quickly approaching the levels of those in the Annex I group of the Kyoto Protocol (i.e., the developed countries excluding the US).
Africa and South America are both fairly small emitters, accounting for 3–4% of global emissions each. Both have emissions almost equal to international aviation and shipping.
Calculations and reporting
Variables There are several ways of measuring greenhouse gas emissions. Some variables that have been reported include: Definition of measurement boundaries: Emissions can be attributed geographically, to the area where they were emitted (the territory principle) or by the activity principle to the territory that produced the emissions. These two principles result in different totals when measuring, for example, electricity importation from one country to another, or emissions at an international airport. Time horizon of different gases: The contribution of given greenhouse gas is reported as a equivalent. The calculation to determine this takes into account how long that gas remains in the atmosphere. This is not always known accurately and calculations must be regularly updated to reflect new information. The measurement protocol itself: This may be via direct measurement or estimation. The four main methods are the emission factor-based method, mass balance method, predictive emissions monitoring systems, and continuous emissions monitoring systems. These methods differ in accuracy, cost, and usability. Public information from space-based measurements of carbon dioxide by Climate Trace is expected to reveal individual large plants before the 2021 United Nations Climate Change Conference.
These measures are sometimes used by countries to assert various policy/ethical positions on climate change.The use of different measures leads to a lack of comparability, which is problematic when monitoring progress towards targets. There are arguments for the adoption of a common measurement tool, or at least the development of communication between different tools.
Reporting Emissions may be tracked over long time periods, known as historical or cumulative emissions measurements. Cumulative emissions provide some indicators of what is responsible for greenhouse gas atmospheric concentration build-up.
National accounts balance