![Worldwide CO2 Emissions](https://upload.wikimedia.org/wikipedia/commons/8/8b/Worldwide_CO2_Emissions.svg)
Greenhouse gas emissions from human activities strengthen the
greenhouse effect
The greenhouse effect is a process that occurs when energy from a planet's host star goes through the planet's atmosphere and heats the planet's surface, but greenhouse gases in the atmosphere prevent some of the heat from returning directly ...
, contributing to
climate change
In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...
. Most is
carbon dioxide
Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...
from burning
fossil fuels:
coal
Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen.
Coal is formed when ...
,
oil
An oil is any nonpolar chemical substance that is composed primarily of hydrocarbons and is hydrophobic (does not mix with water) & lipophilic (mixes with other oils). Oils are usually flammable and surface active. Most oils are unsaturated ...
, and
natural gas
Natural gas (also called fossil gas or simply gas) is a naturally occurring mixture of gaseous hydrocarbons consisting primarily of methane in addition to various smaller amounts of other higher alkanes. Low levels of trace gases like carbo ...
. The
largest emitters include
coal in China and
large oil and gas companies, many
state-owned by OPEC and Russia. Human-caused emissions have increased
atmospheric carbon dioxide
Carbon dioxide in Earth's atmosphere is a trace gas that plays an integral part in the greenhouse effect, carbon cycle, photosynthesis and oceanic carbon cycle. It is one of several greenhouse gases in Earth's atmosphere that are contributin ...
by about 50% over pre-industrial levels. The growing levels of emissions have varied, but it was consistent among all greenhouse gases (GHG). Emissions in the 2010s averaged 56 billion tons a year, higher than ever before.
Electricity generation
Electricity generation is the process of generating electric power from sources of primary energy. For utilities in the electric power industry, it is the stage prior to its delivery ( transmission, distribution, etc.) to end users or its s ...
and
transport
Transport (in British English), or transportation (in American English), is the intentional movement of humans, animals, and goods from one location to another. Modes of transport include air, land ( rail and road), water, cable, pipelin ...
are major emitters; the largest single source, according to the United States Environmental Protection Agency, is transportation, accounting for 27% of all USA greenhouse gas emissions.
Deforestation
Deforestation or forest clearance is the removal of a forest or stand of trees from land that is then converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban use. The most concentrated ...
and other changes in land use also emit carbon dioxide and
methane
Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Ea ...
. The largest source of anthropogenic
methane emissions
Increasing methane emissions are a major contributor to the rising concentration of greenhouse gases in Earth's atmosphere, and are responsible for up to one-third of near-term global heating. During 2019, about 60% (360 million tons) of methane r ...
is
agriculture
Agriculture or farming is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled people t ...
, closely followed by
gas venting and
fugitive emissions
Fugitive emissions are leaks and other irregular releases of gases or vapors from a pressurized containment – such as appliances, storage tanks, pipelines, wells, or other pieces of equipment – mostly from industrial activities. In addition ...
from the
fossil-fuel industry. The largest agricultural methane source is
livestock
Livestock are the domesticated animals raised in an agricultural setting to provide labor and produce diversified products for consumption such as meat, eggs, milk, fur, leather, and wool. The term is sometimes used to refer solely to animal ...
.
Agricultural soils emit
nitrous oxide
Nitrous oxide (dinitrogen oxide or dinitrogen monoxide), commonly known as laughing gas, nitrous, or nos, is a chemical compound, an oxide of nitrogen with the formula . At room temperature, it is a colourless non-flammable gas, and has ...
partly due to
fertilizer
A fertilizer (American English) or fertiliser (British English; see spelling differences) is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from ...
s. Similarly,
fluorinated gases from
refrigerants play an outsized role in total human emissions.
At current emission rates averaging six and a half tonnes per person per year, before 2030 temperatures may have increased by an average of 1.5
°C
The degree Celsius is the unit of temperature on the Celsius scale (originally known as the centigrade scale outside Sweden), one of two temperature scales used in the International System of Units (SI), the other being the Kelvin scale. The ...
(2.7
°F) over pre-industrial levels, which is the limit for the
G7 countries and aspirational limit of the
Paris Agreement.
Measurements and calculations
![Data on climate change around the world](https://upload.wikimedia.org/wikipedia/commons/8/86/Data_on_climate_change_around_the_world.png)
]
Global
greenhouse gas emissions are about 50 Gt per year (6.6t per person) and for 2019 have been estimated at 57 Gt eq including 5 Gt due to land use change. In 2019, approximately 34%
0 Gt-eqof total net anthropogenic GHG emissions came from the energy supply sector, 24%
4 Gt-eqfrom industry, 22%
3 Gt-eq
3 (three) is a number, numeral and digit. It is the natural number following 2 and preceding 4, and is the smallest odd prime number and the only prime preceding a square number. It has religious or cultural significance in many soci ...
rom agriculture, forestry and other land use (AFOLU), 15%
.7 Gt-eqfrom transport and 6%
.3 Gt-eqfrom buildings.
Carbon dioxide
Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...
(), nitrous oxide (),
methane
Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Ea ...
, three groups of
fluorinated gases (
sulfur hexafluoride (),
hydrofluorocarbons
Hydrofluorocarbons (HFCs) are man-made organic compounds that contain fluorine and hydrogen atoms, and are the most common type of organofluorine compounds. Most are gases at room temperature and pressure. They are frequently used in air conditi ...
(HFCs) and
perfluorocarbons
Fluorocarbons are chemical compounds with carbon-fluorine bonds. Compounds that contain many C-F bonds often has distinctive properties, e.g., enhanced stability, volatility, and hydrophobicity. Fluorocarbons and their derivatives are commerci ...
(PFCs)) are the major anthropogenic greenhouse gases, and are regulated under the
Paris Agreement.
[
][
]
Although
CFCs
Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are fully or partly halogenated hydrocarbons that contain carbon (C), hydrogen (H), chlorine (Cl), and fluorine (F), produced as volatile derivatives of methane, ethane, and propan ...
are greenhouse gases, they are regulated by the
Montreal Protocol
The Montreal Protocol is an international treaty designed to protect the ozone layer by phasing out the production of numerous substances that are responsible for ozone depletion. It was agreed on 16 September 1987, and entered into force o ...
, which was motivated by CFCs' contribution to
ozone depletion rather than by their contribution to global warming. Note that 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
The United Nations Environment Programme (UNEP) is responsible for coordinating responses to environmental issues within the United Nations system. It was established by Maurice Strong, its first director, after the United Nations Conference on th ...
reached a legally binding accord to phase out
hydrofluorocarbons
Hydrofluorocarbons (HFCs) are man-made organic compounds that contain fluorine and hydrogen atoms, and are the most common type of organofluorine compounds. Most are gases at room temperature and pressure. They are frequently used in air conditi ...
(HFCs) in the
Kigali Amendment
The Kigali Amendment to the Montreal Protocol is an international agreement to gradually reduce the consumption and production of hydrofluorocarbons (HFCs). It is a legally binding agreement designed to create rights and obligations in internatio ...
to the
Montreal Protocol
The Montreal Protocol is an international treaty designed to protect the ozone layer by phasing out the production of numerous substances that are responsible for ozone depletion. It was agreed on 16 September 1987, and entered into force o ...
.
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 system
Continuous emission monitoring systems (CEMS) are used as a tool to monitor the effluent gas streams resulting from combustion in industrial processes. CEMS can measure flue gas for oxygen, carbon monoxide and carbon dioxide to provide informati ...
s. These methods differ in accuracy, cost, and usability. Public information from
space-based measurements of carbon dioxide
Space-based measurements of carbon dioxide () are used to help answer questions about Earth's carbon cycle. There are a variety of active and planned instruments for measuring carbon dioxide in Earth's atmosphere from space. The first satellite ...
by
Climate Trace
Climate TRACE (Tracking Real-Time Atmospheric Carbon Emissions) is an independent group which monitors and publishes greenhouse gas emissions within weeks. It launched in 2021 before COP26, and improves monitoring, reporting and verification (M ...
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.
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.
[
]
The national accounts balance tracks emissions based on the difference between a country's exports and imports. For many richer nations, the balance is negative because more goods are imported than they are exported. This result is mostly due to the fact that it is cheaper to produce goods outside of developed countries, leading developed countries to become increasingly dependent on services and not goods. A positive account balance would mean that more production was occurring within a country, so more operational factories would increase carbon emission levels.
Emissions may also be measured across shorter time periods. Emissions changes may, for example, be measured against the base year of 1990. 1990 was used in the
United Nations Framework Convention on Climate Change
The United Nations Framework Convention on Climate Change (UNFCCC) established an international environmental treaty to combat "dangerous human interference with the climate system", in part by stabilizing greenhouse gas concentrations in ...
(UNFCCC) as the base year for emissions, and is also used in the
Kyoto Protocol (some gases are also measured from the year 1995).
A country's emissions may also be reported as a proportion of global emissions for a particular year.
Another measurement is of per capita emissions. This divides a country's total annual emissions by its mid-year population.
[
] Per capita emissions may be based on historical or annual emissions.
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.
At current emission rates, before 2030 temperatures may have increased by 1.5
°C
The degree Celsius is the unit of temperature on the Celsius scale (originally known as the centigrade scale outside Sweden), one of two temperature scales used in the International System of Units (SI), the other being the Kelvin scale. The ...
(2.7
°F) over pre-industrial levels, which is the limit for the
G7 countries and aspirational limit of the
Paris Agreement.
Overview of main sources
![Global Carbon Emissions](https://upload.wikimedia.org/wikipedia/commons/4/44/Global_Carbon_Emissions.svg)
Since about 1750, human activity has increased the concentration of carbon dioxide and other greenhouse gases. As of 2021, measured atmospheric concentrations of carbon dioxide were almost 50% higher than pre-industrial levels. Natural sources of carbon dioxide are more than 20 times greater than sources due to human activity, but over periods longer than a few years natural sources are closely balanced by natural sinks, mainly
photosynthesis
Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored i ...
of carbon compounds by plants and marine
plankton
Plankton are the diverse collection of organisms found in water (or air) that are unable to propel themselves against a current (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a crucia ...
. Absorption of terrestrial infrared radiation by longwave absorbing gases makes Earth a less efficient emitter. Therefore, in order for Earth to emit as much energy as is absorbed, global temperatures must increase.
Burning fossil fuels is estimated to have emitted 62% of 2015 human GhG. The largest single source is coal-fired power stations, with 20% of GHG as of 2021.
The main sources of greenhouse gases due to human activity are:
* burning of fossil fuels and deforestation leading to higher carbon dioxide concentrations in the air.
* land use change (mainly deforestation in the tropics) accounts for about a quarter of total anthropogenic GHG emissions.
* livestock
enteric fermentation
Enteric fermentation is a digestive process by which carbohydrates are broken down by microorganisms into simple molecules for absorption into the bloodstream of an animal. Because of human agricultural reliance in many parts of the world on anima ...
and
manure management,
paddy
rice
Rice is the seed of the grass species '' Oryza sativa'' (Asian rice) or less commonly ''Oryza glaberrima'' (African rice). The name wild rice is usually used for species of the genera '' Zizania'' and '' Porteresia'', both wild and domesticat ...
farming, land use and
wetland
A wetland is a distinct ecosystem that is flooded or saturated by water, either permanently (for years or decades) or seasonally (for weeks or months). Flooding results in oxygen-free (anoxic) processes prevailing, especially in the soils. The p ...
changes, man-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
Atmospheric methane is the methane present in Earth's atmosphere. Atmospheric methane concentrations are of interest because it is one of the most potent greenhouse gases in Earth's atmosphere. Atmospheric methane is rising.
The 20-year globa ...
.
* use of
chlorofluorocarbons
Chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) are fully or partly halogenated hydrocarbons that contain carbon (C), hydrogen (H), chlorine (Cl), and fluorine (F), produced as volatile derivatives of methane, ethane, and propa ...
(CFCs) in
refrigeration
The term refrigeration refers to the process of removing heat from an enclosed space or substance for the purpose of lowering the temperature.International Dictionary of Refrigeration, http://dictionary.iifiir.org/search.phpASHRAE Terminology, ht ...
systems, and use of CFCs and
halons in
fire suppression
Wildfire suppression is a range of firefighting tactics used to suppress wildfires. Firefighting efforts in wild land areas require different techniques, equipment, and training from the more familiar structure fire fighting found in populated ...
systems and manufacturing processes.
* agricultural activities, including the use of fertilizers, that lead to higher
nitrous oxide
Nitrous oxide (dinitrogen oxide or dinitrogen monoxide), commonly known as laughing gas, nitrous, or nos, is a chemical compound, an oxide of nitrogen with the formula . At room temperature, it is a colourless non-flammable gas, and has ...
() concentrations.
The major sources of Greenhouse gases (GHG) are:
* Land Use ( emissions)
* Forestry (-LULUCF)
* Nitrous Acid (N2O)
* Fluorinated gases (F-gases)
* Compromising hydrofluorocarbons (HFCs)
* Perfluorocarbons (PFCs)
* sulphur hexafluoride (SF6)
* nitrogen trifluoride (NF3)
The seven sources of from fossil fuel combustion are (with percentage contributions for 2000–2004):
[
* Liquid fuels (e.g., gasoline, fuel oil): 36%
* Solid fuels (e.g., coal): 35%
* Gaseous fuels (e.g., natural gas): 20%
* Cement production: 3%
* Flaring gas industrially and at wells: 1%
* Non-fuel ]hydrocarbon
In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ...
s: 1%
* "International bunker fuels" of transport not included in national inventories: 4%
The largest source of anthropogenic methane emissions
Increasing methane emissions are a major contributor to the rising concentration of greenhouse gases in Earth's atmosphere, and are responsible for up to one-third of near-term global heating. During 2019, about 60% (360 million tons) of methane r ...
is agriculture
Agriculture or farming is the practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary human civilization, whereby farming of domesticated species created food surpluses that enabled people t ...
, closely followed by gas venting and fugitive emissions
Fugitive emissions are leaks and other irregular releases of gases or vapors from a pressurized containment – such as appliances, storage tanks, pipelines, wells, or other pieces of equipment – mostly from industrial activities. In addition ...
from the fossil-fuel industry. The largest agricultural methane source is livestock
Livestock are the domesticated animals raised in an agricultural setting to provide labor and produce diversified products for consumption such as meat, eggs, milk, fur, leather, and wool. The term is sometimes used to refer solely to animal ...
. 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. Agricultural soils emit nitrous oxide
Nitrous oxide (dinitrogen oxide or dinitrogen monoxide), commonly known as laughing gas, nitrous, or nos, is a chemical compound, an oxide of nitrogen with the formula . At room temperature, it is a colourless non-flammable gas, and has ...
partly due to fertilizer
A fertilizer (American English) or fertiliser (British English; see spelling differences) is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from ...
s.
*
* ()
* (F-gases)
* (HFCs)
* (PFCs)
* (SF6)
*
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.
Emissions by type of energy source
Relative emission from various fuels
One liter of gasoline, when used as a fuel, produces (about 1300 liters or 1.3 cubic meters) of carbon dioxide, a greenhouse gas. One US gallon produces 19.4 lb (1,291.5 gallons or 172.65 cubic feet).
The mass of carbon dioxide that is released when one MJ of energy is released from fuel can be estimated to a good approximation. For the chemical formula of diesel we use as an approximation . Note that diesel is a mixture of different molecules. As carbon has a molar mass of 12 g/mol and hydrogen (atomic!) has a molar mass of about 1 g/mol, so the fraction by weight of carbon in diesel is roughly 12/14. The reaction of diesel combustion is given by:
2 + 3n 2n + 2n
Carbon dioxide has a molar mass of 44g/mol as it consists of 2 atoms of oxygen (16 g/mol) and 1 atom of carbon (12 g/mol). So 12 g of carbon yield 44 g of Carbon dioxide. Diesel has an energy content of 42.6 MJ per kg or 23.47 gram of Diesel contain 1 MJ of energy. Putting everything together the mass of carbon dioxide that is produced by releasing 1MJ of energy from diesel fuel can be calculated as:
For gasoline, with 22 g/MJ and a ratio of carbon to hydrogen atoms of about 6 to 14, the estimated value of carbon emission for 1MJ of energy is:
Emissions by type of greenhouse gas
Carbon dioxide
Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...
() is the dominant emitted greenhouse gas, while methane
Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Ea ...
() emissions almost have the same short-term impact. Nitrous oxide
Nitrous oxide (dinitrogen oxide or dinitrogen monoxide), commonly known as laughing gas, nitrous, or nos, is a chemical compound, an oxide of nitrogen with the formula . At room temperature, it is a colourless non-flammable gas, and has ...
(N2O) and fluorinated gases (F-Gases) play a minor role.
GHG emissions are measured in equivalents determined by their global warming potential
Global warming potential (GWP) is the heat absorbed by any greenhouse gas in the atmosphere, as a multiple of the heat that would be absorbed by the same mass of carbon dioxide (). GWP is 1 for . For other gases it depends on the gas and the time ...
(GWP), which depends on their lifetime in the atmosphere. Estimations largely depend on the ability of oceans and land sinks to absorb these gases. Short-lived climate pollutants (SLCPs) including methane
Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Ea ...
, hydrofluorocarbons (HFCs), tropospheric ozone
Ground-level ozone (O3), also known as surface-level ozone and tropospheric ozone, is a trace gas in the troposphere (the lowest level of the Earth's atmosphere), with an average concentration of 20–30 parts per billion by volume (ppbv), with c ...
and black carbon
Chemically, black carbon (BC) is a component of fine particulate matter (PM ≤ 2.5 µm in aerodynamic diameter). Black carbon consists of pure carbon in several linked forms. It is formed through the incomplete combustion of fossil fuel ...
persist in the atmosphere for a period ranging from days to 15 years; whereas carbon dioxide can remain in the atmosphere for millennia. Reducing SLCP emissions can cut the ongoing rate of global warming by almost half and reduce the projected Arctic warming by two-thirds.
GHG emissions in 2019 were estimated at 57.4 Gte, while emissions alone made up 42.5 Gt including land-use change (LUC).[using 100 year ]global warming potential
Global warming potential (GWP) is the heat absorbed by any greenhouse gas in the atmosphere, as a multiple of the heat that would be absorbed by the same mass of carbon dioxide (). GWP is 1 for . For other gases it depends on the gas and the time ...
from IPCC-AR4
While mitigation measures for decarbonization
Climate change mitigation is action to limit climate change by reducing emissions of greenhouse gases or removing those gases from the atmosphere. The recent rise in global average temperature is mostly caused by emissions from fossil fuels b ...
are essential on the longer-term, they could result in weak near-term warming because sources of carbon emissions often also co-emit air pollution. Hence, pairing measures that target carbon dioxide with measures targeting non- pollutants – short-lived climate pollutants, which have faster effects on the climate, is essential for climate goals.
Carbon dioxide ()
* Fossil fuel: oil
An oil is any nonpolar chemical substance that is composed primarily of hydrocarbons and is hydrophobic (does not mix with water) & lipophilic (mixes with other oils). Oils are usually flammable and surface active. Most oils are unsaturated ...
, gas
Gas is one of the four fundamental states of matter (the others being solid, liquid, and plasma).
A pure gas may be made up of individual atoms (e.g. a noble gas like neon), elemental molecules made from one type of atom (e.g. oxygen), or ...
and coal
Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen.
Coal is formed when ...
(89%) are the major driver of anthropogenic global warming with annual emissions of 35.6 Gt in 2019.[Olivier J.G.J. and Peters J.A.H.W. (2020)]
Trends in global CO2 and total greenhouse gas emissions: 2020 report
PBL Netherlands
Environmental Assessment Agency, The Hague.
* Cement
A cement is a binder, a chemical substance used for construction that sets, hardens, and adheres to other materials to bind them together. Cement is seldom used on its own, but rather to bind sand and gravel ( aggregate) together. Cement mi ...
production (4%) is estimated at 1.42 Gt
* Land-use change (LUC) is the imbalance of deforestation
Deforestation or forest clearance is the removal of a forest or stand of trees from land that is then converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban use. The most concentrated ...
and reforestation
Reforestation (occasionally, reafforestation) is the natural or intentional restocking of existing forests and woodlands (forestation) that have been depleted, usually through deforestation, but also after clearcutting.
Management
A debat ...
. Estimations are very uncertain at 4.5 Gt. Wildfire
A wildfire, forest fire, bushfire, wildland fire or rural fire is an unplanned, uncontrolled and unpredictable fire in an area of combustible vegetation. Depending on the type of vegetation present, a wildfire may be more specifically identi ...
s alone cause annual emissions of about 7 Gt
* Non-energy use of fuels, carbon losses in coke ovens, and flaring in crude oil production.
Methane (CH4)
Methane has a high immediate impact with a 5-year global warming potential
Global warming potential (GWP) is the heat absorbed by any greenhouse gas in the atmosphere, as a multiple of the heat that would be absorbed by the same mass of carbon dioxide (). GWP is 1 for . For other gases it depends on the gas and the time ...
of up to 100. Given this, the current 389 Mt of methane emissions has about the same short-term global warming effect as emissions, with a risk to trigger irreversible changes in climate and ecosystems. For methane, a reduction of about 30% below current emission levels would lead to a stabilization in its atmospheric concentration.
* Fossil fuels (32%), again, account for most of the methane emissions including coal mining (12% of methane total), gas distribution and leakages (11%) as well as gas venting in oil production (9%).
* Livestock (28%) with cattle (21%) as the dominant source, followed by buffalo (3%), sheep (2%), and goats (1.5%).
* Human waste and wastewater (21%): When biomass waste in landfills and organic substances in domestic and industrial wastewater
Industrial wastewater treatment describes the processes used for Wastewater treatment, treating wastewater that is produced by industries as an undesirable by-product. After treatment, the treated industrial wastewater (or effluent) may be reuse ...
is decomposed by bacteria in anaerobic conditions, substantial amounts of methane are generated.
* Rice cultivation (10%) on flooded rice fields is another agricultural source, where anaerobic decomposition of organic material produces methane.
Nitrous oxide ()
N2O has a high GWP and significant Ozone Depleting Potential. It is estimated that the global warming potential of N2O over 100 years is 265 times greater than CO2. For N2O, a reduction of more than 50% would be required for a stabilization.
* Most emissions (56%) by agriculture, especially meat production: cattle (droppings on pasture), fertilizers, animal manure.
* Combustion of fossil fuels (18%) and bio fuels.
* Industrial production of adipic acid
Adipic acid or hexanedioic acid is the organic compound with the formula (CH2)4(COOH)2. From an industrial perspective, it is the most important dicarboxylic acid: about 2.5 billion kilograms of this white crystalline powder are produced annuall ...
and nitric acid
Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available nitri ...
.
F-Gases
Fluorinated gases include hydrofluorocarbons
Hydrofluorocarbons (HFCs) are man-made organic compounds that contain fluorine and hydrogen atoms, and are the most common type of organofluorine compounds. Most are gases at room temperature and pressure. They are frequently used in air conditi ...
(HFC), perfluorocarbons (PFC), sulfur hexafluoride (SF6), and nitrogen trifluoride (NF3). They are used by switchgear in the power sector, semiconductor manufacture, aluminium production and a large unknown source of SF6. Continued phase down of manufacture and use of HFCs under the Kigali Amendment
The Kigali Amendment to the Montreal Protocol is an international agreement to gradually reduce the consumption and production of hydrofluorocarbons (HFCs). It is a legally binding agreement designed to create rights and obligations in internatio ...
to the Montreal Protocol
The Montreal Protocol is an international treaty designed to protect the ozone layer by phasing out the production of numerous substances that are responsible for ozone depletion. It was agreed on 16 September 1987, and entered into force o ...
will help reduce HFC emissions and concurrently improve the energy efficiency of appliances that use HFCs like air conditioners, freezers and other refrigeration devices.
Black carbon
Black carbon
Chemically, black carbon (BC) is a component of fine particulate matter (PM ≤ 2.5 µm in aerodynamic diameter). Black carbon consists of pure carbon in several linked forms. It is formed through the incomplete combustion of fossil fuel ...
is formed through the incomplete combustion of fossil fuels, biofuel, and biomass. It is not a greenhouse gas but a climate forcing
Earth's climate system is a complex system having five interacting components: the atmosphere (air), the hydrosphere (water), the cryosphere (ice and permafrost), the lithosphere (earth's upper rocky layer) and the biosphere (living things). ''C ...
agent. Black carbon can absorb sunlight and reduce albedo
Albedo (; ) is the measure of the diffuse reflection of solar radiation out of the total solar radiation and measured on a scale from 0, corresponding to a black body that absorbs all incident radiation, to 1, corresponding to a body that refl ...
when deposited on snow and ice. Indirect heating can be caused by the interaction with clouds. Black carbon stays in the atmosphere for only several days to weeks. Emissions may be mitigated by upgrading coke ovens, installing particulate filters on diesel-based engines, reducing routine flaring
Routine flaring, also known as production flaring, is a method and current practice of disposing of large unwanted amounts of associated petroleum gas (APG) during crude oil extraction. The gas is first separated from the liquids and solids d ...
, and minimizing open burning of biomass.
Emissions by sector
Global greenhouse gas emissions can be attributed to different sectors of the economy. This provides a picture of the varying contributions of different types of economic activity to climate change, and helps in understanding the changes required to mitigate climate change.
Manmade greenhouse gas emissions can be divided into those that arise from the combustion of fuels to produce energy, and those generated by other processes. Around two thirds of greenhouse gas emissions arise from the combustion of fuels.
Energy may be produced at the point of consumption, or by a generator for consumption by others. Thus emissions arising from energy production may be categorized according to where they are emitted, or where the resulting energy is consumed. If emissions are attributed at the point of production, then electricity generators contribute about 25% of global greenhouse gas emissions. If these emissions are attributed to the final consumer then 24% of total emissions arise from manufacturing and construction, 17% from transportation, 11% from domestic consumers, and 7% from commercial consumers. Around 4% of emissions arise from the energy consumed by the energy and fuel industry itself.
The remaining third of emissions arise from processes other than energy production. 12% of total emissions arise from agriculture, 7% from land use change and forestry, 6% from industrial processes, and 3% from waste.
Electricity generation
Coal-fired power stations are the single largest emitter, with over 20% of global GhG in 2018. Although much less polluting than coal plants, natural gas-fired power plant
A gas-fired power plant or gas-fired power station or natural gas power plant is a thermal power station which burns natural gas to generate electricity. Natural gas power stations generate almost a quarter of world electricity and a signifi ...
s are also major emitters, taking electricity generation as a whole over 25% in 2018. Notably, just 5% of the world's power plants account for almost three-quarters of carbon emissions from electricity generation, based on an inventory of more than 29,000 fossil-fuel power plants across 221 countries. In the 2022 IPCC report, it is noted that providing modern energy services universally would only increase greenhouse gas emissions by a few percent at most. This slight increase means that the additional energy demand that comes from supporting decent living standards for all would be far lower than current average energy consumption.
Agriculture, forestry and land use
Agriculture
= Deforestation
=
Deforestation is a major source of greenhouse gas emissions. A study shows annual carbon emissions (or carbon loss) from tropical deforestation
Deforestation or forest clearance is the removal of a forest or stand of trees from land that is then converted to non-forest use. Deforestation can involve conversion of forest land to farms, ranches, or urban use. The most concentrated ...
have doubled during the last two decades and continue to increase. (0.97 ±0.16 PgC per year in 2001–2005 to 1.99 ±0.13 PgC per year in 2015–2019)
= Land-use change
=
Land-use change, e.g., the clearing of forests for agricultural use, can affect the concentration of greenhouse gases in the atmosphere by altering how much carbon flows out of the atmosphere into carbon sink
A carbon sink is anything, natural or otherwise, that accumulates and stores some carbon-containing chemical compound for an indefinite period and thereby removes carbon dioxide () from the atmosphere.
Globally, the two most important carbon si ...
s. Accounting for land-use change can be understood as an attempt to measure "net" emissions, i.e., gross emissions from all sources minus the removal of emissions from the atmosphere by carbon sinks.
There are substantial uncertainties in the measurement of net carbon emissions. Additionally, there is controversy over how carbon sinks should be allocated between different regions and over time. For instance, concentrating on more recent changes in carbon sinks is likely to favour those regions that have deforested earlier, e.g., Europe.
In 1997, human-caused Indonesian peat fires were estimated to have released between 13% and 40% of the average annual global carbon emissions caused by the burning of fossil fuels.
Transport
Aviation
Approximately 3.5% of the overall human impacts on climate are from the aviation sector. The impact of the sector on climate in the late 20 years had doubled, but the part of the contribution of the sector in comparison to other sectors did not change because other sectors grew as well.
Trucking and haulage
Over a quarter of global transport emissions are from road freight, so many countries are further restricting truck
A truck or lorry is a motor vehicle designed to transport cargo, carry specialized payloads, or perform other utilitarian work. Trucks vary greatly in size, power, and configuration, but the vast majority feature body-on-frame constructi ...
emissions to help limit climate change.
Buildings and construction
In 2018, manufacturing construction materials and maintaining buildings accounted for 39% of carbon dioxide emissions from energy and process-related emissions. Manufacture of glass, cement, and steel accounted for 11% of energy and process-related emissions. Because building construction is a significant investment, more than two-thirds of buildings in existence will still exist in 2050. Retrofitting existing buildings to become more efficient will be necessary to meet the targets of the Paris Agreement; it will be insufficient to only apply low-emission standards to new construction. Buildings that produce as much energy as they consume are called zero-energy building
A Zero Energy Building (ZEB), also known as a Net Zero Energy (NZE) building, is a building with net zero energy consumption, meaning the total amount of energy used by the building on an annual basis is equal to the amount of renewable energy ...
s, while buildings that produce more than they consume are energy-plus. Low-energy buildings are designed to be highly efficient with low total energy consumption and carbon emissions—a popular type is the passive house
"Passive house" (german: Passivhaus) is a voluntary standard for energy efficiency in a building, which reduces the building's ecological footprint. It results in ultra-low energy buildings that require little energy for space heating or coo ...
.
The global design and construction industry is responsible for approximately 39 percent of greenhouse gas emissions. Green building practices that avoid emissions or capture the carbon already present in the environment, allow for reduced footprint of the construction industry, for example, use of hempcrete, cellulose fiber insulation, and landscaping
Landscaping refers to any activity that modifies the visible features of an area of land, including the following:
# Living elements, such as flora or fauna; or what is commonly called gardening, the art and craft of growing plants with a goal ...
.
In 2019, the building sector was responsible for 12 Gt-eq emissions. More than 95% of these emissions were carbon, and the remaining 5% were and halocarbon.
Industrial processes
Secunda CTL
Secunda CTL is a synthetic fuel plant owned by Sasol at Secunda, Mpumalanga in South Africa. It uses coal liquefaction to produce petroleum-like synthetic crude oil from coal. The process used by Sasol is based on the Fischer–Tropsch process. ...
is the world's largest single emitter, at 56.5 million tonnes a year.
Around 6% of emissions are fugitive emissions, which are waste gases released by the extraction of fossil fuels.
Steel and aluminum
Steel and aluminum are key economic sectors for the carbon capture and storage
Carbon capture and storage (CCS) or carbon capture and sequestration is the process of capturing carbon dioxide (CO2) before it enters the atmosphere, transporting it, and storing it (carbon sequestration) for centuries or millennia. Usually th ...
. According to a 2013 study, "in 2004, the steel industry along emits about 590M tons of , which accounts for 5.2% of the global anthropogenic GHG emissions. emitted from steel production primarily comes from energy consumption of fossil fuel as well as the use of limestone
Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...
to purify iron oxides."
Plastics
Plastics are produced mainly from fossil fuels. It was estimated that between 3% and 4% of global GHG emissions are associated with plastics' life cycles. The EPA estimates as many as five mass units of carbon dioxide are emitted for each mass unit of polyethylene terephthalate (PET) produced—the type of plastic most commonly used for beverage bottles, the transportation produce greenhouse gases also. Plastic waste emits carbon dioxide when it degrades. In 2018 research claimed that some of the most common plastics in the environment release the greenhouse gases methane
Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Ea ...
and ethylene when exposed to sunlight in an amount that can affect the earth climate.
Due to the lightness of plastic versus glass or metal, plastic may reduce energy consumption. For example, packaging beverages in PET plastic rather than glass or metal is estimated to save 52% in transportation energy, if the glass or metal package is single-use
A disposable (also called disposable product) is a product designed for a single use after which it is recycled or is disposed as solid waste. The term is also sometimes used for products that may last several months (e.g. disposable air filte ...
, of course.
In 2019 a new report "Plastic and Climate" was published. According to the report, the production and incineration of plastics will contribute in the equivalent of 850 million tonnes of carbon dioxide
Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...
() to the atmosphere in 2019. With the current trend, annual life cycle greenhouse gas emissions of plastics will grow to 1.34 billion tonnes by 2030. By 2050, the life cycle emissions of plastics could reach 56 billion tonnes, as much as 14 percent of the Earth's remaining carbon budget
A carbon budget is "the maximum amount of cumulative net global anthropogenic carbon dioxide () emissions that would result in limiting global warming to a given level with a given probability, taking into account the effect of other anthropogen ...
. The report says that only solutions which involve a reduction in consumption can solve the problem, while others like biodegradable plastic, ocean cleanup, using renewable energy in plastic industry can do little, and in some cases may even worsen it.
Pulp and paper
The global print and paper industry accounts for about 1% of global carbon dioxide emissions. Greenhouse gas emissions from the pulp and paper industry are generated from the combustion of fossil fuels required for raw material production and transportation, wastewater treatment facilities, purchased power, paper transportation, printed product transportation, disposal and recycling.
Various services
Digital services
In 2020 data centers
A data center (American English) or data centre (British English)See spelling differences. is a building, a dedicated space within a building, or a group of buildings used to house computer systems and associated components, such as telecommun ...
(excluding cryptocurrency mining) and data transmission each used about 1% of world electricity. The digital sector produces between 2% and 4% of global GHG emissions, a large part of which is from chipmaking. However the sector reduces emissions from other sectors which have a larger global share, such as transport of people, and possibly buildings and industry.
Mining for proof-of-work
Proof of work (PoW) is a form of cryptographic proof in which one party (the ''prover'') proves to others (the ''verifiers'') that a certain amount of a specific computational effort has been expended. Verifiers can subsequently confirm this expe ...
cryptocurrencies requires enormous amounts of electricity and consequently comes with a large carbon footprint. Proof-of-work blockchains such as Bitcoin, Ethereum
Ethereum is a decentralized, open-source blockchain with smart contract functionality. Ether (Abbreviation: ETH; sign: Ξ) is the native cryptocurrency of the platform. Among cryptocurrencies, ether is second only to bitcoin in market capita ...
, Litecoin
Litecoin ( Abbreviation: LTC; sign: Ł) is a decentralized peer-to-peer cryptocurrency and open-source software project released under the MIT/X11 license. Inspired by Bitcoin, Litecoin was among the earliest altcoins, starting in October 201 ...
, and Monero
Monero (; Abbreviation: XMR) is a decentralized cryptocurrency. It uses a public distributed ledger with privacy-enhancing technologies that obfuscate transactions to achieve anonymity and fungibility. Observers cannot decipher addresses t ...
were estimated to have added between 3 million and 15 million tonnes of carbon dioxide () to the atmosphere in the period from 1 January 2016 to 30 June 2017. By the end of 2021, Bitcoin was estimated to produce 65.4 million tonnes of , as much as Greece
Greece,, or , romanized: ', officially the Hellenic Republic, is a country in Southeast Europe. It is situated on the southern tip of the Balkans, and is located at the crossroads of Europe, Asia, and Africa. Greece shares land borders ...
, and consume between 91 and 177 terawatt-hours annually. Bitcoin is the least energy-efficient cryptocurrency, using 707.6 kilowatt-hours of electricity per transaction.
Health care
The healthcare sector produces 4.4% - 4.6% of global greenhouse gas emissions.
Water supply and sanitation
Tourism
According to UNEP
The United Nations Environment Programme (UNEP) is responsible for coordinating responses to environmental issues within the United Nations system. It was established by Maurice Strong, its first director, after the United Nations Conference on ...
, global tourism
Tourism is travel for pleasure or business; also the theory and practice of touring, the business of attracting, accommodating, and entertaining tourists, and the business of operating tours. The World Tourism Organization defines tourism mor ...
is a significant contributor to the increasing concentrations of greenhouse gases in the atmosphere.
Emissions by other characteristics
The responsibility for anthropogenic climate change differs substantially among individuals, e.g. between groups or cohorts.
Generational
Researchers report that, on average, played "a leading role
A leading actor, leading actress, or simply lead (), plays the role of the protagonist of a film, television show or play. The word ''lead'' may also refer to the largest role in the piece, and ''leading actor'' may refer to a person who typic ...
in driving up GHG emissions in the past decade and are on the way to becoming the largest contributor" due to factors such as demographic transition
In demography, demographic transition is a phenomenon and theory which refers to the historical shift from high birth rates and high death rates in societies with minimal technology, education (especially of women) and economic development, to l ...
, and high expenditures on carbon-intensive products like energy which is used i.a. for heating rooms and private transport. They are less affected by climate change impacts, but have e.g. the same vote
Voting is a method by which a group, such as a meeting or an Constituency, electorate, can engage for the purpose of making a collective decision making, decision or expressing an opinion usually following discussions, debates or election camp ...
-weights for the available electoral options.
By socio-economic class
Fueled by the consumptive lifestyle of wealthy people, the wealthiest 5% of the global population has been responsible for 37% of the absolute increase in greenhouse gas emissions worldwide. Almost half of the increase in absolute global emissions has been caused by the richest 10% of the population. In the newest report from the IPCC 2022, it states that the lifestyle consumptions of the poor and middle class in emerging economies produce approximately 5–50 times less the amount that the high class in already developed high-income countries.[https://report.ipcc.ch/ar6wg3/pdf/IPCC_AR6_WGIII_SummaryForPolicymakers.pdf ] Variations in regional, and national per capita emissions partly reflect different development stages, but they also vary widely at similar income levels. The 10% of households with the highest per capita emissions contribute a disproportionately large share of global household GHG emissions.
Studies find that the most affluent citizens of the world are responsible for most environmental impacts
Environmental issues are effects of human activity on the biophysical environment, most often of which are harmful effects that cause environmental degradation. Environmental protection is the practice of protecting the natural environment on t ...
, and robust action by them is necessary for prospects of moving towards safer environmental conditions.
According to a 2020 report by Oxfam and the Stockholm Environment Institute
The Stockholm Environment Institute, or SEI, is a non-profit, independent research and policy institute specialising in sustainable development and environmental issues, with seven affiliate offices around the world. SEI works on climate change ...
, the richest 1% of the global population have caused twice as much carbon emissions as the poorest 50% over the 25 years from 1990 to 2015. This was, respectively, during that period, 15% of cumulative emissions compared to 7%. The bottom half of the population is directly-responsible for less than 20% of energy footprints and consume less than the top 5% in terms of trade-corrected energy. The largest disproportionality was identified to be in the domain of transport, where e.g. the top 10% consume 56% of vehicle fuel and conduct 70% of vehicle purchases. However, wealthy individuals are also often shareholders and typically have more influence and, especially in the case of billionaires, may also direct lobbying efforts, direct financial decisions, and/or control companies:
Regional and national attribution of emissions
Greenhouse gas intensity
Greenhouse gas intensity is a ratio between greenhouse gas emissions and another metric, e.g., gross domestic product (GDP) or energy use. The terms "carbon intensity" and " emissions intensity" are also sometimes used. Emission intensities may be calculated using market exchange rates (MER) or purchasing power parity (PPP).[ Calculations based on MER show large differences in intensities between developed and developing countries, whereas calculations based on PPP show smaller differences. According to a study discussing the relationship between urbanization and carbon emissions, urbanization is becoming a huge player in the global carbon cycle. Depending on total carbon emissions done by a city that hasn't invested in carbon efficiency or improved resource management, the global carbon cycle is projected to reach 75% of the world population by 2030.
]
Cumulative and historical emissions
Cumulative anthropogenic (i.e., human-emitted) emissions of from fossil fuel use are a major cause of global warming
In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to E ...
, and give some indication of which countries have contributed most to human-induced climate change. In particular, stays in the atmosphere for at least 150 years, whilst methane and nitrous oxides generally disappear within a decade or so. The graph gives some indication of which regions have contributed most to human-induced climate change.
[
] When these numbers are calculated per capita cumulative emissions based on then-current population the situation is shown even more clearly. The ratio in per capita emissions between industrialized countries and developing countries was estimated at more than 10 to 1.
Non-OECD
The Organisation for Economic Co-operation and Development (OECD; french: Organisation de coopération et de développement économiques, ''OCDE'') is an intergovernmental organisation with 38 member countries, founded in 1961 to stimulate e ...
countries accounted for 42% of cumulative energy-related emissions between 1890 and 2007.[
] Over this time period, the US accounted for 28% of emissions; the EU, 23%; Japan, 4%; other OECD countries 5%; Russia, 11%; China, 9%; India, 3%; and the rest of the world, 18%.
Overall, developed countries accounted for 83.8% of industrial emissions over this time period, and 67.8% of total emissions. Developing countries accounted for industrial emissions of 16.2% over this time period, and 32.2% of total emissions.
In comparison, humans have emitted more greenhouse gases than the Chicxulub meteorite impact event which caused the extinction of the dinosaurs
Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...
.
Transport, together with electricity generation
Electricity generation is the process of generating electric power from sources of primary energy. For utilities in the electric power industry, it is the stage prior to its delivery ( transmission, distribution, etc.) to end users or its s ...
, is the major source of greenhouse gas emissions in the EU. Greenhouse gas emissions from the transportation sector continue to rise, in contrast to power generation and nearly all other sectors. Since 1990, transportation emissions have increased by 30%. The transportation sector accounts for around 70% of these emissions. The majority of these emissions are caused by passenger vehicle
A vehicle (from la, vehiculum) is a machine that transports people or cargo. Vehicles include wagons, bicycles, motor vehicles (motorcycles, cars, trucks, buses, mobility scooters for disabled people), railed vehicles (trains, trams), ...
s and vans. Road travel is the first major source of greenhouse gas emissions from transportation, followed by aircraft and maritime. Waterborne transportation is still the least carbon-intensive mode of transportation on average, and it is an essential link in sustainable multimodal freight supply chains.
Buildings, like industry, are directly responsible for around one-fifth of greenhouse gas emissions, primarily from space heating
Heating, ventilation, and air conditioning (HVAC) is the use of various technologies to control the temperature, humidity, and purity of the air in an enclosed space. Its goal is to provide thermal comfort and acceptable indoor air quality. HV ...
and hot water consumption. When combined with power consumption within buildings, this figure climbs to more than one-third.
Within the EU, the agricultural sector presently accounts for roughly 10% of total greenhouse gas emissions, with methane
Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Ea ...
from livestock accounting for slightly more than half of 10%.
Estimates of total emissions do include biotic carbon emissions, mainly from deforestation. Including biotic emissions brings about the same controversy mentioned earlier regarding carbon sinks and land-use change.[ The actual calculation of net emissions is very complex, and is affected by how carbon sinks are allocated between regions and the dynamics of the ]climate system
Earth's climate system is a complex system having five interacting components: the atmosphere (air), the hydrosphere (water), the cryosphere (ice and permafrost), the lithosphere (earth's upper rocky layer) and the biosphere (living things). '' ...
.
The graphic shows the logarithm of 1850–2019 fossil fuel emissions; natural log on left, actual value of Gigatons per year on right. Although emissions increased during the 170-year period by about 3% per year overall, intervals of distinctly different growth rates (broken at 1913, 1945, and 1973) can be detected. The regression lines suggest that emissions can rapidly shift from one growth regime to another and then persist for long periods of time. The most recent drop in emissions growth - by almost 3 percentage points - was at about the time of the 1970s energy crisis
The 1970s energy crisis occurred when the Western world, particularly the United States, Canada, Western Europe, Australia, and New Zealand, faced substantial petroleum shortages as well as elevated prices. The two worst crises of this period wer ...
. Percent changes per year were estimated by piecewise linear regression on the log data and are shown on the plot; the data are from The Integrated Carbon Observation system.
Changes since a particular base year
The sharp acceleration in emissions since 2000 to more than a 3% increase per year (more than 2 ppm per year) from 1.1% per year during the 1990s is attributable to the lapse of formerly declining trends in carbon intensity
An emission intensity (also carbon intensity or C.I.) is the emission rate of a given pollutant relative to the intensity of a specific activity, or an industrial production process; for example grams of carbon dioxide released per megajoule o ...
of both developing and developed nations. China was responsible for most of global growth in emissions during this period. Localised plummeting emissions associated with the collapse of the Soviet Union have been followed by slow emissions growth in this region due to more efficient energy use, made necessary by the increasing proportion of it that is exported. In comparison, methane has not increased appreciably, and by 0.25% y−1.
Using different base years for measuring emissions has an effect on estimates of national contributions to global warming. This can be calculated by dividing a country's highest contribution to global warming starting from a particular base year, by that country's minimum contribution to global warming starting from a particular base year. Choosing between base years of 1750, 1900, 1950, and 1990 has a significant effect for most countries. Within the G8 group of countries, it is most significant for the UK, France and Germany. These countries have a long history of emissions (see the section on Cumulative and historical emissions).
Embedded emissions
One way of attributing greenhouse gas emissions is to measure the embedded emissions
One way of attributing greenhouse gas (GHG) emissions is to measure the embedded emissions of goods that are being consumed (also referred to as "embodied emissions", "embodied carbon emissions", or "embodied carbon"). This is different from the ...
(also referred to as "embodied emissions") of goods that are being consumed. Emissions are usually measured according to production, rather than consumption. For example, in the main international treaty
A treaty is a formal, legally binding written agreement between actors in international law. It is usually made by and between sovereign states, but can include international organizations, individuals, business entities, and other legal pe ...
on climate change (the UNFCCC
The United Nations Framework Convention on Climate Change (UNFCCC) established an international environmental treaty to combat "dangerous human interference with the climate system", in part by stabilizing greenhouse gas concentrations in th ...
), countries report on emissions produced within their borders, e.g., the emissions produced from burning fossil fuels.[
] Under a production-based accounting of emissions, embedded emissions on imported goods are attributed to the exporting, rather than the importing, country. Under a consumption-based accounting of emissions, embedded emissions on imported goods are attributed to the importing country, rather than the exporting, country.
Davis and Caldeira (2010) found that a substantial proportion of emissions are traded internationally. The net effect of trade was to export emissions from China and other emerging markets to consumers in the US, Japan, and Western Europe.
Historical trends
The Integrated Carbon Observation System (ICOS) continuously releases data about emissions, budget and concentration at individual observation stations.
By country
Annual emissions
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). Other countries with fast growing emissions are South Korea
South Korea, officially the Republic of Korea (ROK), is a country in East Asia, constituting the southern part of the Korean Peninsula and sharing a land border with North Korea. Its western border is formed by the Yellow Sea, while its eas ...
, Iran, and Australia (which apart from the oil rich Persian Gulf states, now has the highest per capita emission rate in the world). On the other hand, annual per capita emissions of the EU-15 and the US are gradually decreasing over time. Emissions in Russia and Ukraine have decreased fastest since 1990 due to economic restructuring in these countries.
Energy statistics for fast-growing economies are less accurate than those for industrialized countries.
The greenhouse gas footprint refers to the emissions resulting from the creation of products or services. It is more comprehensive than the commonly used carbon footprint, which measures only carbon dioxide, one of many greenhouse gases.
2015 was the first year to see both total global economic growth and a reduction of carbon emissions.
Top emitter countries
In 2019, China, the United States, India, the EU27+UK, Russia, and Japan - the world's largest emitters - together accounted for 51% of the population, 62.5% of global gross domestic product, 62% of total global fossil fuel consumption and emitted 67% of total global fossil . Emissions from these five countries and the EU28 show different changes in 2019 compared to 2018: the largest relative increase is found for China (+3.4%), followed by India (+1.6%). On the contrary, the EU27+UK (-3.8%), the United States (-2.6%), Japan (-2.1%) and Russia (-0.8%) reduced their fossil emissions.[
]
United States
China
India
Reducing greenhouse gas emissions
Fiscal decentralisation and carbon reductions
As carbon oxides are one important source of greenhouse gas, having means to reduce it is important. One suggestion, is to consider some means in relation to fiscal decentralisation. Previous research found that the linear term of fiscal decentralization promotes carbon emissions, while the non-linear term mitigates it. It verified the inverted U-shaped curve between fiscal decentralization and carbon emissions. Besides, increasing energy prices for non-renewable energy decrease carbon emission due to a substitution effect. Among other explanatory variables, improvement in the quality of institutions decreases carbon emissions, while the gross domestic product increases it. Strengthening fiscal decentralization, lowering non-renewable energy prices, and improving institutional quality to check the deteriorating environmental quality in the study sample and other worldwide regions can reduce carbon emissions.
Effect of policy
Government
A government is the system or group of people governing an organized community, generally a state.
In the case of its broad associative definition, government normally consists of legislature, executive, and judiciary. Government is ...
s have taken action to reduce greenhouse gas emissions to mitigate climate change. Assessments of policy effectiveness have included work by the Intergovernmental Panel on Climate Change, International Energy Agency, and United Nations Environment Programme
The United Nations Environment Programme (UNEP) is responsible for coordinating responses to environmental issues within the United Nations system. It was established by Maurice Strong, its first director, after the United Nations Conference on th ...
. Policies implemented by governments have included[
][
] national and regional targets to reduce emissions, promoting energy efficiency
Energy efficiency may refer to:
* Energy efficiency (physics), the ratio between the useful output and input of an energy conversion process
** Electrical efficiency, useful power output per electrical power consumed
** Mechanical efficiency, a ra ...
, and support for a renewable energy transition, such as Solar energy, as an effective use of renewable energy because solar uses energy from the sun and does not release pollutants into the air.
Countries and regions listed in Annex I of the United Nations Framework Convention on Climate Change
The United Nations Framework Convention on Climate Change (UNFCCC) established an international environmental treaty to combat "dangerous human interference with the climate system", in part by stabilizing greenhouse gas concentrations in ...
(UNFCCC) (i.e., the OECD and former planned economies of the Soviet Union) are required to submit periodic assessments to the UNFCCC of actions they are taking to address climate change.
Projections
Impacts of the COVID-19 pandemic
In 2020, carbon dioxide emissions
Greenhouse gas emissions from human activities strengthen the greenhouse effect, contributing to climate change. Most is carbon dioxide from burning fossil fuels: coal, oil, and natural gas. The largest emitters include coal in China and la ...
fell by 6.4% or 2.3 billion tonnes globally. In April 2020, emissions fell by up to 30%. In China, lockdowns and other measures resulted in a 26% decrease in coal consumption, and a 50% reduction in nitrogen oxide emissions. Greenhouse gas emissions rebounded later in the pandemic as many countries began lifting restrictions, with the direct impact of pandemic policies having a negligible long-term impact on climate change. However, decreased human activity during the pandemic diverted attention from ongoing activities such as accelerated deforestation of the Amazon rainforest
The Amazon rainforest is the largest rainforest in the world, covering an area of 3,000,000 km2 (2,316,612.95 square miles). It represents over half of the planet's rainforests and comprises the largest and most biodiverse tract of tropi ...
. The hindrance of environmental policy efforts, combined with economic slowdown may have contributed to slowed investment in green energy
Energy is sustainable if it "meets the needs of the present without compromising the ability of future generations to meet their own needs". Most definitions of sustainable energy include considerations of environmental aspects such as greenh ...
technologies.
See also
* Attribution of recent climate change
Efforts to scientifically ascertain and attribute mechanisms responsible for recent global warming and related climate changes on Earth have found that the main driver is elevated levels of greenhouse gases produced by human activities, with ...
* Carbon accounting
Greenhouse gas accounting or Carbon accounting is a framework of methods to measure and track how much greenhouse gas (GHG) an organization emits or takes actions to reduce. Corporations, cities and other groups use these techniques to help limi ...
* Carbon credit
A carbon credit is a generic term for any tradable certificate or permit representing the right to emit a set amount of carbon dioxide or the equivalent amount of a different greenhouse gas (tCO2e).
Carbon credits and carbon markets are a compo ...
* Carbon Dioxide Information Analysis Center
The Carbon Dioxide Information Analysis Center (CDIAC) was an organization within the United States Department of Energy that had the primary responsibility for providing the US government and research community with global warming data and analysi ...
* Carbon offset
A carbon offset is a reduction or removal of emissions of carbon dioxide or other greenhouse gases made in order to compensate for emissions made elsewhere. Offsets are measured in tonnes of carbon dioxide-equivalent (CO2e). One ton of carb ...
* Carbon tax
A carbon tax is a tax levied on the carbon emissions required to produce goods and services. Carbon taxes are intended to make visible the "hidden" social costs of carbon emissions, which are otherwise felt only in indirect ways like more sev ...
* Green hydrogen
Green hydrogen (GH2 or GH2) is hydrogen generated by renewable energy or from low-carbon power.
Green hydrogen has significantly lower carbon emissions than grey hydrogen, which is produced by steam reforming of natural gas, which makes up the b ...
* List of countries by renewable electricity production
This article is a list of countries and territories by electricity generation from renewable sources every year. Note that most countries import and/or export electricity, so the percentage figure do not reflect the percentage of consumption tha ...
* Low-carbon economy
A low-carbon economy (LCE) or decarbonised economy is an economy based on energy sources that produce low levels of greenhouse gas (GHG) emissions. GHG emissions due to human activity are the dominant cause of observed climate change since the mi ...
* Orbiting Carbon Observatory 2
Orbiting Carbon Observatory-2 (OCO-2) is an American environmental science satellite which launched on 2 July 2014. A NASA mission, it is a replacement for the Orbiting Carbon Observatory which was lost in a launch failure in 2009. It is the secon ...
* Paris Agreement
* Perfluorotributylamine
Perfluorotributylamine (PFTBA), also referred to as FC43, is a colorless liquid with the formula N(C4F9)3. The compound consists of three butyl groups connected to an amine center, in which all of the hydrogen atoms have been replaced with fluori ...
* Vehicle emission standard
Emission standards are the legal requirements governing air pollutants released into the atmosphere. Emission standards set quantitative limits on the permissible amount of specific air pollutants that may be released from specific sources over ...
* World energy supply and consumption
World energy supply and consumption is global production and preparation of fuel, generation of electricity, energy transport, and energy consumption. It is a basic part of economic activity. It includes heat, but not energy from food.
This art ...
* Zero-emissions vehicle
A zero-emission vehicle, or ZEV, is a vehicle that does not emit exhaust gas or other pollutants from the onboard source of power. The California definition also adds that this includes under any and all possible operational modes and conditions ...
References
External links
The official greenhouse gas emissions data of developed countries
from the UNFCCC
The United Nations Framework Convention on Climate Change (UNFCCC) established an international environmental treaty to combat "dangerous human interference with the climate system", in part by stabilizing greenhouse gas concentrations in th ...
Annual Greenhouse Gas Index (AGGI)
from NOAA
NOAA CMDL CCGG – Interactive Atmospheric Data Visualization
NOAA data
IPCC Website
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Official IPCC Sixth Assessment Report website
{{DEFAULTSORT:Greenhouse Gas
Articles containing video clips
Climate forcing