Greenhouse gas emissions

This article is about emissions of greenhouse gases into the atmosphere. For carbon dioxide emissions once they are in the atmosphere, see Carbon dioxide in Earth's atmosphere. For the effect of greenhouse gases once in the atmosphere, see greenhouse effect. For characteristics of greenhouse gases themselves, see greenhouse gas.

2020 Worldwide CO2 emissions (by region, per capita); variwide diagram

Annual greenhouse gas emissions per person (height of vertical bars) and per country (area inside vertical bars)

In the highest-emitting countries, emission trends in recent decades sometimes diverge from longer-term historical trends.

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 large oil and gas companies, many state-owned by OPEC and Russia. Human-caused emissions have increased atmospheric carbon dioxide 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 and transport are major emitters, the largest single source being coal-fired power stations with 20% of GHG. 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.

At current emission rates averaging six and a half tonnes per person per year, before 2030 temperatures may have increased by 1.5 °C (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

Annual CO₂ emissions, total by country, not per capita (2017 data)

Data from:[1] [2] [3]

Global GHG Emissions by gas

Global greenhouse gas emissions are about 50 Gt per year (6.6t per person) and for 2019 have been estimated at 57 Gt CO₂ eq including 5 Gt due to land use change. In 2019, approximately 34% [20 GtCO₂-eq] of total net anthropogenic GHG emissions came from the energy supply sector, 24% [14 GtCO₂-eq] from industry, 22% [13 GtCO₂-eq]from agriculture, forestry and other land use (AFOLU), 15% [8.7 GtCO₂-eq] from transport and 6% [3.3 GtCO₂-eq] from buildings.

Carbon dioxide (CO₂), nitrous oxide (N
₂O), methane, three groups of fluorinated gases (sulfur hexafluoride (SF
₆), hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs)) are the major anthropogenic greenhouse gases, and are regulated under the Paris Agreement.

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. 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 reached a legally binding accord to phase out hydrofluorocarbons (HFCs) in the Kigali Amendment to the Montreal Protocol.

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 CO₂ 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.

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 (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 (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

See also: Effects of climate change on ecosystems

Modern global CO₂ emissions from the burning of fossil fuels.

Potential CO₂ emissions from large fossil fuel projects 'carbon bombs' per country

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 of carbon compounds by plants and marine plankton. 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 and manure management, paddy rice farming, land use and wetland 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.
• use of chlorofluorocarbons (CFCs) in refrigeration systems, and use of CFCs and halons in fire suppression systems and manufacturing processes.
• agricultural activities, including the use of fertilizers, that lead to higher nitrous oxide (N
  ₂O) concentrations.

The seven sources of CO₂ from fossil fuel combustion are (with percentage contributions for 2000–2004):

This list needs updating, as it uses an out-of-date source. See the 2019 IPCC report for newer data.

• 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 hydrocarbons: 1%  
• "International bunker fuels" of transport not included in national inventories: 4%

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. Agricultural soils emit nitrous oxide partly due to fertilizers.

The major sources of Greenhouse gases (GHG) are:

• Land Use (CO₂ emissions)
• Forestry (CO₂-LULUCF)
• Nitrous Acid (N₂O)
• Fluorinated gases (F-gases)
• Compromising hydrofluorocarbons (HFCs)
• Perfluorocarbons (PFCs)
• sulphur hexafluoride (SF6)
• nitrogen trifluoride (NF3)

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 energy source

This section is an excerpt from Life-cycle greenhouse gas emissions of energy sources § Global warming potential of selected electricity sources.[edit]

Life-cycle greenhouse gas emissions of electricity supply technologies, median values calculated by IPCC

Life cycle CO₂ equivalent (including albedo effect) from selected electricity supply technologies according to IPCC 2014. Arranged by decreasing median (gCO₂eq/kWh) values.

Technology	Min.	Median	Max.
Currently commercially available technologies
Coal – PC	740	820	910
Gas – combined cycle	410	490	650
Biomass – Dedicated	130	230	420
Solar PV – Utility scale	18	48	180
Solar PV – rooftop	26	41	60
Geothermal	6.0	38	79
Concentrated solar power	8.8	27	63
Hydropower	1.0	24	22001
Wind Offshore	8.0	12	35
Nuclear	3.7	12	110
Wind Onshore	7.0	11	56
Pre‐commercial technologies
Ocean (Tidal and wave)	5.6	17	28

¹ see also environmental impact of reservoirs#Greenhouse gases.

Lifecycle GHG emissions, in g CO₂ eq. per kWh, UNECE 2020

Lifecycle CO₂ emissions per kWh, EU28 countries, according to UNECE 2020.

Technology		gCO2eq/kWh
Hard coal	PC, without CCS	1000
	IGCC, without CCS	850
	SC, without CCS	950
	PC, with CCS	370
	IGCC, with CCS	280
	SC, with CCS	330
Natural gas	NGCC, without CCS	430
	NGCC, with CCS	130
Hydro	660 MW	150
	360 MW	11
Nuclear	average	5.1
CSP	tower	22
	trough	42
PV	poly-Si, ground-mounted	37
	poly-Si, roof-mounted	37
	CdTe, ground-mounted	12
	CdTe, roof-mounted	15
	CIGS, ground-mounted	11
	CIGS, roof-mounted	14
Wind	onshore	12
	offshore, concrete foundation	14
	offshore, steel foundation	13

List of acronyms:

• PC — pulverized coal
• CCS — carbon capture and storage
• IGCC — integrated gasification combined cycle
• SC — supercritical
• NGCC — natural gas combined cycle
• CSP — concentrated solar power
• PV — photovoltaic power

Relative CO₂ emission from various fuels

One liter of gasoline, when used as a fuel, produces 2.32 kg (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 C
_nH
_2n. 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:

2C
_nH
_2n + 3nO
₂ ⇌ 2nCO
₂ + 2nH
₂O

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:

$23.47\ \mathrm {g} {\text{ (Diesel)}}/\mathrm {MJ} \cdot {\frac {12}{14}}\cdot {\frac {44}{12}}=74\ \mathrm {g} {\text{ (carbon dioxide)}}/\mathrm {MJ}$

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:

$22\ \mathrm {g} {\text{ (gasoline)}}/\mathrm {MJ} \cdot {\frac {6\cdot 12}{6\cdot 12+14\cdot 1}}\cdot {\frac {44}{12}}=67.5\ \mathrm {g} {\text{ (carbon dioxide)}}/\mathrm {MJ}$

Mass of carbon dioxide emitted per quantity of energy for various fuels

Fuel name	CO2 emitted (lbs/106 Btu)	CO2 emitted (g/MJ)	CO2 emitted (g/kWh)
Hydrogen gas	0	0.0	0.0
Natural gas	117	50.30	181.08
Liquefied petroleum gas	139	59.76	215.14
Propane	139	59.76	215.14
Aviation gasoline	153	65.78	236.81
Automobile gasoline	156	67.07	241.45
Kerosene	159	68.36	246.10
Fuel oil	161	69.22	249.19
Tires/tire derived fuel	189	81.26	292.54
Wood and wood waste	195	83.83	301.79
Coal (bituminous)	205	88.13	317.27
Coal (sub-bituminous)	213	91.57	329.65
Coal (lignite)	215	92.43	332.75
Petroleum coke	225	96.73	348.23
Tar-sand bitumen
Coal (anthracite)	227	97.59	351.32

Emissions by greenhouse gas

See also: List of greenhouse gases

GHG emissions 2019 by gas type
without land-use change
using 100 year GWP
Total: 51.8 GtCO₂e

  CO₂ mostly by fossil fuel (72%)

  CH₄ methane (19%)

  N
₂O nitrous oxide (6%)

  Fluorinated gases (3%)

CO₂ emissions by fuel type

  coal (39%)

  oil (34%)

  gas (21%)

  cement (4%)

  others (1.5%)

Carbon dioxide (CO₂) is the dominant emitted greenhouse gas, while methane (CH₄) emissions almost have the same short-term impact. Nitrous oxide (N₂O) and fluorinated gases (F-Gases) play a minor role.

GHG emissions are measured in CO₂ equivalents determined by their global warming potential (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, hydrofluorocarbons (HFCs), tropospheric ozone and black carbon 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 GtCO₂e, while CO₂ emissions alone made up 42.5 Gt including land-use change (LUC).

While mitigation measures for decarbonization 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-CO₂ pollutants – short-lived climate pollutants, which have faster effects on the climate, is essential for climate goals.

Carbon dioxide (CO₂)

• Fossil fuel: oil, gas and coal (89%) are the major driver of anthropogenic global warming with annual emissions of 35.6 GtCO₂ in 2019.
• Cement production (4%) is estimated at 1.42 GtCO₂
• Land-use change (LUC) is the imbalance of deforestation and reforestation. Estimations are very uncertain at 4.5 GtCO₂. Wildfires alone cause annual emissions of about 7 GtCO₂
• Non-energy use of fuels, carbon losses in coke ovens, and flaring in crude oil production.

Methane (CH₄)

Historical and future temperature projections showing importance of mitigating short-lived climate pollutants like methane

Methane has a high immediate impact with a 5-year global warming potential of up to 100. Given this, the current 389 Mt of methane emissions has about the same short-term global warming effect as CO₂ 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 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 (N
₂O)

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 and nitric acid.

F-Gases

Fluorinated gases include hydrofluorocarbons (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 to the Montreal Protocol 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 is formed through the incomplete combustion of fossil fuels, biofuel, and biomass. It is not a greenhouse gas but a climate forcing agent. Black carbon can absorb sunlight and reduce albedo 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, and minimizing open burning of biomass.

Emissions by sector

Greenhouse Gas Emissions by Economic Sector according to IPCC Fifth Assessment Report

2016 global greenhouse gas emissions by sector. Percentages are calculated from estimated global emissions of all Kyoto Greenhouse Gases, converted to CO₂ equivalent quantities (GtCO₂e).

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 global warming, 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. Around 6% of emissions are fugitive emissions, which are waste gases released by the extraction of fossil fuels.

As of 2020 Secunda CTL is the world's largest single emitter, at 56.5 million tonnes CO₂ a year.

Agriculture

This section is an excerpt from Greenhouse gas emissions from agriculture.[edit]

The amount of greenhouse gas emissions from agriculture is significant: The agriculture, forestry and land use sector contribute between 13% and 21% of global greenhouse gas emissions. Emissions come from direct greenhouse gas emissions (for example from rice production and livestock farming). and from indirect emissions. With regards to direct emissions, nitrous oxide and methane make up over half of total greenhouse gas emission from agriculture. Indirect emissions on the other hand come from the conversion of non-agricultural land such as forests into agricultural land. Furthermore, there is also fossil fuel consumption for transport and fertilizer production. For example, the manufacture and use of nitrogen fertilizer contributes around 5% of all global greenhouse gas emissions. Livestock farming is a major source of greenhouse gas emissions. At the same time, livestock farming is affected by climate change.

Farm animals' digestive systems can be put into two categories: monogastric and ruminant. Ruminant cattle for beef and dairy rank high in greenhouse gas emissions. In comparison, monogastric, or pigs and poultry-related foods, are lower. The consumption of the monogastric types may yield less emissions. Monogastric animals have a higher feed-conversion efficiency, and also do not produce as much methane. Non-ruminant livestock, such as poultry, emit far fewer greenhouse gases.

There are many strategies to reduce greenhouse gas emissions from agriculture (this is one of the goals of climate-smart agriculture). Mitigation measures in the food system can be divided into four categories. These are demand-side changes, ecosystem protections, mitigation on farms, and mitigation in supply chains. On the demand side, limiting food waste is an effective way to reduce food emissions. Changes to a diet less reliant on animal products such as plant-based diets are also effective. This could include milk substitutes and meat alternatives. Several methods are also under investigation to reduce the greenhouse gas emissions from livestock farming. These include genetic selection, introduction of methanotrophic bacteria into the rumen, vaccines, feeds, diet modification and grazing management.

Aviation

Further information: Environmental effects of 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.

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 buildings, 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.

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.

In 2019, the building sector was responsible for 12 GtCO₂-eq emissions. More than 95% of these emissions were carbon, and the remaining 5% were CH₄ N₂O and halocarbon.

Digital sector

Drip irrigation providing water to turmeric crop.

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.

Health care

The healthcare sector produces 4.4% - 4.6% of global greenhouse gas emissions.

Steel and aluminum

Steel and aluminum are key economic sectors for the carbon capture and storage. According to a 2013 study, "in 2004, the steel industry along emits about 590M tons of CO₂, which accounts for 5.2% of the global anthropogenic GHG emissions. CO₂ emitted from steel production primarily comes from energy consumption of fossil fuel as well as the use of limestone to purify iron oxides."

Electricity generation

See also: Life-cycle greenhouse gas emissions of energy sources

Global greenhouse gas emissions by gas.

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 plants 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.

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 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, 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 (CO₂) 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. 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.

Sanitation sector

Wastewater as well as sanitation systems are known to contribute to greenhouse-gas emissions (GHG) mainly through the breakdown of excreta during the treatment process. This results in the generation of methane gas, that is then released into the environment. Emissions from the sanitation and wastewater sector have been focused mainly on treatment systems, particularly treatment plants, and this accounts for the bulk of the carbon footprint for the sector.

In as much as climate impacts from wastewater and sanitation systems present global risks, low-income countries experience greater risks in many cases. In recent years, attention to adaptation needs within the sanitation sector is just beginning to gain momentum.

Tourism

According to UNEP, global tourism is a significant contributor to the increasing concentrations of greenhouse gases in the atmosphere.

Trucking and haulage

Over a quarter of global transport CO₂ emissions are from road freight, so many countries are further restricting truck CO₂ emissions to help limit climate change.

Deforestation

Mean annual carbon loss from tropical deforestation.

Further information: Deforestation § Atmospheric, and Deforestation and climate change

Deforestation is a major source of greenhouse gas emissions. A study shows annual carbon emissions (or carbon loss) from tropical deforestation 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)

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, the elderly played "a leading role 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, low informed concern about climate change 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-weights for the available electoral options.

By socio-economic class

The emissions of the richest 1% of the global population account for more than twice the combined share of the poorest 50%. Compliance with the 1.5°C goal of the Paris Agreement would require the richest 1% to reduce their current emissions by at least a factor of 30, while per-person emissions of the poorest 50% could increase by a factor of about 3.

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. 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, 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 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

See also: Greenhouse gas inventory

From land-use change

Main article: Greenhouse gas emissions from agriculture

Substantial land-use change contributions to emissions have been made by Latin America, Southeast Asia, Africa, and Pacific Islands. Area of rectangles shows total emissions for that region.

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 sinks. 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.

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 CO₂ emission by world region

Cumulative per person emissions by world region in 3 time periods

CO₂ Emissions by source since 1880

Cumulative anthropogenic (i.e., human-emitted) emissions of CO₂ from fossil fuel use are a major cause of global warming, and give some indication of which countries have contributed most to human-induced climate change. In particular, CO₂ 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 countries accounted for 42% of cumulative energy-related CO₂ 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 CO₂ emissions over this time period, and 67.8% of total CO₂ emissions. Developing countries accounted for industrial CO₂ emissions of 16.2% over this time period, and 32.2% of total CO₂ emissions.

In comparison, humans have emitted more greenhouse gases than the Chicxulub meteorite impact event which caused the extinction of the dinosaurs.

Transport, together with electricity generation, 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 vehicles 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 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 from livestock accounting for slightly more than half of 10%.

Estimates of total CO₂ 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.

Fossil fuel CO₂ emissions on a log (natural and base 10) scale

The graphic shows the logarithm of 1850–2019 fossil fuel CO₂ 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. 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

See also: Greenhouse gas inventory

The sharp acceleration in CO₂ 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 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 N
₂O 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 CO₂ emissions (see the section on Cumulative and historical emissions).

Embedded emissions

One way of attributing greenhouse gas emissions is to measure the embedded emissions (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 on climate change (the UNFCCC), 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 CO₂ 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.

By country

Main article: List of countries by greenhouse gas emissions

Annual emissions

CO₂ emissions vs GDP

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, 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

The top 40 countries emitting all greenhouse gases, showing both that derived from all sources including land clearance and forestry and also the CO₂ component excluding those sources. Per capita figures are included. "World Resources Institute data".. Note that Indonesia and Brazil show very much higher than on graphs simply showing fossil fuel use.

See also: List of countries by carbon dioxide emissions, List of countries by carbon dioxide emissions per capita, List of countries by greenhouse gas emissions, and List of countries by greenhouse gas emissions per person

In 2019, China, the United States, India, the EU27+UK, Russia, and Japan - the world's largest CO₂ 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 CO₂. 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 CO₂ emissions.

2019 Fossil CO₂ emissions by country

Country	total emissions (Mton)	Share (%)	per capita (ton)	per GDP (ton/k$)
Global Total	38,016.57	100.00	4.93	0.29
China	11,535.20	30.34	8.12	0.51
United States	5,107.26	13.43	15.52	0.25
EU27+UK	3,303.97	8.69	6.47	0.14
India	2,597.36	6.83	1.90	0.28
Russia	1,792.02	4.71	12.45	0.45
Japan	1,153.72	3.03	9.09	0.22
International Shipping	730.26	1.92	-	-
Germany	702.60	1.85	8.52	0.16
Iran	701.99	1.85	8.48	0.68
South Korea	651.87	1.71	12.70	0.30
International Aviation	627.48	1.65	-	-
Indonesia	625.66	1.65	2.32	0.20
Saudi Arabia	614.61	1.62	18.00	0.38
Canada	584.85	1.54	15.69	0.32
South Africa	494.86	1.30	8.52	0.68
Mexico	485.00	1.28	3.67	0.19
Brazil	478.15	1.26	2.25	0.15
Australia	433.38	1.14	17.27	0.34
Turkey	415.78	1.09	5.01	0.18
United Kingdom	364.91	0.96	5.45	0.12
Italy, San Marino and the Holy See	331.56	0.87	5.60	0.13
Poland	317.65	0.84	8.35	0.25
France and Monaco	314.74	0.83	4.81	0.10
Vietnam	305.25	0.80	3.13	0.39
Kazakhstan	277.36	0.73	14.92	0.57
Taiwan	276.78	0.73	11.65	0.23
Thailand	275.06	0.72	3.97	0.21
Spain and Andorra	259.31	0.68	5.58	0.13
Egypt	255.37	0.67	2.52	0.22
Malaysia	248.83	0.65	7.67	0.27
Pakistan	223.63	0.59	1.09	0.22
United Arab Emirates	222.61	0.59	22.99	0.34
Argentina	199.41	0.52	4.42	0.20
Iraq	197.61	0.52	4.89	0.46
Ukraine	196.40	0.52	4.48	0.36
Algeria	180.57	0.47	4.23	0.37
Netherlands	156.41	0.41	9.13	0.16
Philippines	150.64	0.40	1.39	0.16
Bangladesh	110.16	0.29	0.66	0.14
Venezuela	110.06	0.29	3.36	0.39
Qatar	106.53	0.28	38.82	0.41
Czechia	105.69	0.28	9.94	0.25
Belgium	104.41	0.27	9.03	0.18
Nigeria	100.22	0.26	0.50	0.10
Kuwait	98.95	0.26	23.29	0.47
Uzbekistan	94.99	0.25	2.90	0.40
Oman	92.78	0.24	18.55	0.67
Turkmenistan	90.52	0.24	15.23	0.98
Chile	89.89	0.24	4.90	0.20
Colombia	86.55	0.23	1.74	0.12
Romania	78.63	0.21	4.04	0.14
Morocco	73.91	0.19	2.02	0.27
Austria	72.36	0.19	8.25	0.14
Serbia and Montenegro	70.69	0.19	7.55	0.44
Israel and Palestine	68.33	0.18	7.96	0.18
Belarus	66.34	0.17	7.03	0.37
Greece	65.57	0.17	5.89	0.20
Peru	56.29	0.15	1.71	0.13
Singapore	53.37	0.14	9.09	0.10
Hungary	53.18	0.14	5.51	0.17
Libya	52.05	0.14	7.92	0.51
Portugal	48.47	0.13	4.73	0.14
Myanmar	48.31	0.13	0.89	0.17
Norway	47.99	0.13	8.89	0.14
Sweden	44.75	0.12	4.45	0.08
Hong Kong	44.02	0.12	5.88	0.10
Finland	43.41	0.11	7.81	0.16
Bulgaria	43.31	0.11	6.20	0.27
North Korea	42.17	0.11	1.64	0.36
Ecuador	40.70	0.11	2.38	0.21
Switzerland and Liechtenstein	39.37	0.10	4.57	0.07
New Zealand	38.67	0.10	8.07	0.18
Ireland	36.55	0.10	7.54	0.09
Slovakia	35.99	0.09	6.60	0.20
Azerbaijan	35.98	0.09	3.59	0.25
Mongolia	35.93	0.09	11.35	0.91
Bahrain	35.44	0.09	21.64	0.48
Bosnia and Herzegovina	33.50	0.09	9.57	0.68
Trinidad and Tobago	32.74	0.09	23.81	0.90
Tunisia	32.07	0.08	2.72	0.25
Denmark	31.12	0.08	5.39	0.09
Cuba	31.04	0.08	2.70	0.11
Syria	29.16	0.08	1.58	1.20
Jordan	28.34	0.07	2.81	0.28
Sri Lanka	27.57	0.07	1.31	0.10
Lebanon	27.44	0.07	4.52	0.27
Dominican Republic	27.28	0.07	2.48	0.14
Angola	25.82	0.07	0.81	0.12
Bolivia	24.51	0.06	2.15	0.24
Sudan and South Sudan	22.57	0.06	0.40	0.13
Guatemala	21.20	0.06	1.21	0.15
Kenya	19.81	0.05	0.38	0.09
Croatia	19.12	0.05	4.62	0.16
Estonia	18.50	0.05	14.19	0.38
Ethiopia	18.25	0.05	0.17	0.07
Ghana	16.84	0.04	0.56	0.10
Cambodia	16.49	0.04	1.00	0.23
New Caledonia	15.66	0.04	55.25	1.67
Slovenia	15.37	0.04	7.38	0.19
Nepal	15.02	0.04	0.50	0.15
Lithuania	13.77	0.04	4.81	0.13
Côte d’Ivoire	13.56	0.04	0.53	0.10
Georgia	13.47	0.04	3.45	0.24
Tanzania	13.34	0.04	0.22	0.09
Kyrgyzstan	11.92	0.03	1.92	0.35
Panama	11.63	0.03	2.75	0.09
Afghanistan	11.00	0.03	0.30	0.13
Yemen	10.89	0.03	0.37	0.17
Zimbabwe	10.86	0.03	0.63	0.26
Honduras	10.36	0.03	1.08	0.19
Cameroon	10.10	0.03	0.40	0.11
Senegal	9.81	0.03	0.59	0.18
Luxembourg	9.74	0.03	16.31	0.14
Mozambique	9.26	0.02	0.29	0.24
Moldova	9.23	0.02	2.29	0.27
Costa Rica	8.98	0.02	1.80	0.09
North Macedonia	8.92	0.02	4.28	0.26
Tajikistan	8.92	0.02	0.96	0.28
Paraguay	8.47	0.02	1.21	0.09
Latvia	8.38	0.02	4.38	0.14
Benin	8.15	0.02	0.69	0.21
Mauritania	7.66	0.02	1.64	0.33
Zambia	7.50	0.02	0.41	0.12
Jamaica	7.44	0.02	2.56	0.26
Cyprus	7.41	0.02	6.19	0.21
El Salvador	7.15	0.02	1.11	0.13
Botswana	7.04	0.02	2.96	0.17
Brunei	7.02	0.02	15.98	0.26
Laos	6.78	0.02	0.96	0.12
Uruguay	6.56	0.02	1.89	0.09
Armenia	5.92	0.02	2.02	0.15
Curaçao	5.91	0.02	36.38	1.51
Nicaragua	5.86	0.02	0.92	0.17
Congo	5.80	0.02	1.05	0.33
Albania	5.66	0.01	1.93	0.14
Uganda	5.34	0.01	0.12	0.06
Namibia	4.40	0.01	1.67	0.18
Mauritius	4.33	0.01	3.41	0.15
Madagascar	4.20	0.01	0.16	0.09
Papua New Guinea	4.07	0.01	0.47	0.11
Iceland	3.93	0.01	11.53	0.19
Puerto Rico	3.91	0.01	1.07	0.04
Barbados	3.83	0.01	13.34	0.85
Burkina Faso	3.64	0.01	0.18	0.08
Haiti	3.58	0.01	0.32	0.18
Gabon	3.48	0.01	1.65	0.11
Equatorial Guinea	3.47	0.01	2.55	0.14
Réunion	3.02	0.01	3.40	-
Democratic Republic of the Congo	2.98	0.01	0.03	0.03
Guinea	2.92	0.01	0.22	0.09
Togo	2.85	0.01	0.35	0.22
Bahamas	2.45	0.01	6.08	0.18
Niger	2.36	0.01	0.10	0.08
Bhutan	2.12	0.01	2.57	0.24
Suriname	2.06	0.01	3.59	0.22
Martinique	1.95	0.01	5.07	-
Guadeloupe	1.87	0.00	4.17	-
Malawi	1.62	0.00	0.08	0.08
Guyana	1.52	0.00	1.94	0.20
Sierra Leone	1.40	0.00	0.18	0.10
Fiji	1.36	0.00	1.48	0.11
Palau	1.33	0.00	59.88	4.09
Macao	1.27	0.00	1.98	0.02
Liberia	1.21	0.00	0.24	0.17
Rwanda	1.15	0.00	0.09	0.04
Eswatini	1.14	0.00	0.81	0.11
Djibouti	1.05	0.00	1.06	0.20
Seychelles	1.05	0.00	10.98	0.37
Malta	1.04	0.00	2.41	0.05
Mali	1.03	0.00	0.05	0.02
Cabo Verde	1.02	0.00	1.83	0.26
Somalia	0.97	0.00	0.06	0.57
Maldives	0.91	0.00	2.02	0.09
Chad	0.89	0.00	0.06	0.04
Aruba	0.78	0.00	7.39	0.19
Eritrea	0.75	0.00	0.14	0.08
Lesotho	0.75	0.00	0.33	0.13
Gibraltar	0.69	0.00	19.88	0.45
French Guiana	0.61	0.00	2.06	-
French Polynesia	0.60	0.00	2.08	0.10
The Gambia	0.59	0.00	0.27	0.11
Greenland	0.54	0.00	9.47	0.19
Antigua and Barbuda	0.51	0.00	4.90	0.24
Central African Republic	0.49	0.00	0.10	0.11
Guinea-Bissau	0.44	0.00	0.22	0.11
Cayman Islands	0.40	0.00	6.38	0.09
Timor-Leste	0.38	0.00	0.28	0.10
Belize	0.37	0.00	0.95	0.14
Bermuda	0.35	0.00	5.75	0.14
Burundi	0.34	0.00	0.03	0.04
Saint Lucia	0.30	0.00	1.65	0.11
Western Sahara	0.30	0.00	0.51	-
Grenada	0.23	0.00	2.10	0.12
Comoros	0.21	0.00	0.25	0.08
Saint Kitts and Nevis	0.19	0.00	3.44	0.14
São Tomé and Príncipe	0.16	0.00	0.75	0.19
Saint Vincent and the Grenadines	0.15	0.00	1.32	0.11
Samoa	0.14	0.00	0.70	0.11
Solomon Islands	0.14	0.00	0.22	0.09
Tonga	0.13	0.00	1.16	0.20
Turks and Caicos Islands	0.13	0.00	3.70	0.13
British Virgin Islands	0.12	0.00	3.77	0.17
Dominica	0.10	0.00	1.38	0.12
Vanuatu	0.09	0.00	0.30	0.09
Saint Pierre and Miquelon	0.06	0.00	9.72	-
Cook Islands	0.04	0.00	2.51	-
Falkland Islands	0.03	0.00	10.87	-
Kiribati	0.03	0.00	0.28	0.13
Anguilla	0.02	0.00	1.54	0.12
Saint Helena, Ascension and Tristan da Cunha	0.02	0.00	3.87	-
Faroes	0.00	0.00	0.04	0.00

File:The C-Story of Human Civilization.webm

The C-Story of Human Civilization by PIK

United States

This section is an excerpt from Greenhouse gas emissions by the United States.[edit]

Transportation in the United States is the largest source of greenhouse gas

The United States produced 5.2 billion metric tons of carbon dioxide equivalent greenhouse gas (GHG) emissions in 2020, the second largest in the world after greenhouse gas emissions by China and among the countries with the highest greenhouse gas emissions per person. In 2019 China is estimated to have emitted 27% of world GHG, followed by the United States with 11%, then India with 6.6%. In total the United States has emitted a quarter of world GHG, more than any other country. Annual emissions are over 15 tons per person and, amongst the top eight emitters, is the highest country by greenhouse gas emissions per person. However, the IEA estimates that the richest decile in the US emits over 55 tonnes of CO₂ per capita each year. Because coal-fired power stations are gradually shutting down, in the 2010s emissions from electricity generation fell to second place behind transportation which is now the largest single source. In 2020, 27% of the GHG emissions of the United States were from transportation, 25% from electricity, 24% from industry, 13% from commercial and residential buildings and 11% from agriculture. In 2021, the electric power sector was the second largest source of U.S. greenhouse gas emissions, accounting for 25% of the U.S. total. These greenhouse gas emissions are contributing to climate change in the United States, as well as worldwide.

China

This section is an excerpt from Greenhouse gas emissions by China.[edit]

China has the most total annual emissions (area of rectangle) of any nation, and has higher than average per capita emissions.

Cumulatively over time, emissions from China have caused more economic damage globally than any other nation except the U.S.

China's greenhouse gas emissions are the largest of any country in the world both in production and consumption terms, and stem mainly from coal burning, including coal power, coal mining, and blast furnaces producing iron and steel. When measuring production-based emissions, China emitted over 14 gigatonnes (Gt) CO_2eq of greenhouse gases in 2019, 27% of the world total. When measuring in consumption-based terms, which adds emissions associated with imported goods and extracts those associated with exported goods, China accounts for 13 gigatonnes (Gt) or 25% of global emissions.

These high levels of emissions are due to China's large population; the country's per person emissions have remained considerably lower than those in the developed world. This corresponds to over 10.1 tonnes CO_2eq emitted per person each year, slightly over the world average and the EU average but significantly lower than the second largest emitter of greenhouse gases, the United States, with its 17.6 tonnes per person. Accounting for historic emissions, OECD countries produced four times more CO2 in cumulative emissions than China, due to developed countries' early start in industrialization. Overall, China is a net importer of greenhouse emissions.

The targets laid out in China's nationally determined contribution in 2016 will likely be met, but are not enough to properly combat global warming. China has committed to peak emissions by 2030 and net zero by 2060. In order to limit warming to 1.5 degrees C coal plants in China without carbon capture must be phased out by 2045. China continues to build coal-fired power stations in 2020 and promised to "phase down" coal use from 2026. According to various analysis, China is estimated to overachieve its renewable energy capacity and emission reduction goals early, but long-term plans are still required to combat the global climate change and meeting the Nationally Determined Contribution (NDC) targets.

India

This section is an excerpt from Climate change in India § Greenhouse gas emissions.[edit]

Greenhouse gas emissions by India are the third largest in the world and the main source is coal. India emitted 2.8 Gt of CO_2eq in 2016 (2.5 including LULUCF). 79% were CO₂, 14% methane and 5% nitrous oxide. India emits about 3 gigatonnes (Gt) CO_2eq of greenhouse gases each year; about two tons per person, which is half the world average. The country emits 7% of global emissions.

As of 2019 these figures are quite uncertain, but a comprehensive greenhouse gas inventory is within reach. Cutting greenhouse gas emissions, and therefore air pollution in India, would have health benefits worth 4 to 5 times the cost, which would be the most cost-effective in the world.

The Paris Agreement commitments included a reduction of this intensity by 33–35% by 2030. India's annual emissions per person are less than the global average, and the UNEP forecasts that by 2030 they will be between 3 and 4 tonnes.

In 2019 China is estimated to have emitted 27% of world GhG, followed by the US with 11%, then India with 6.6%.

The Indian national carbon trading scheme may be created in 2023.

Reducing greenhouse gas emissions

This section is an excerpt from Climate change mitigation.[edit]

Climate change mitigation (or decarbonisation) is action to limit the greenhouse gases in the atmosphere that cause climate change. Greenhouse gas emissions are primarily caused by people burning fossil fuels such as coal, oil, and natural gas. Phasing out fossil fuel use can happen by conserving energy and replacing fossil fuels with clean energy sources such as wind, hydro, solar, and nuclear power. Secondary mitigation strategies include changes to land use and removing carbon dioxide (CO₂) from the atmosphere. Governments have pledged to reduce greenhouse gas emissions, but actions to date are insufficient to avoid dangerous levels of climate change.

Solar energy and wind power have the greatest potential for supplanting fossil fuels at the lowest cost compared to other options. The availability of sunshine and wind is variable and can require electrical grid upgrades, such as using long-distance electricity transmission to group a range of power sources. Energy storage can also be used to even out power output, and demand management can limit power use when power generation is low. Cleanly generated electricity can usually replace fossil fuels for powering transportation, heating buildings, and running industrial processes. Certain processes are more difficult to decarbonise, such as air travel and cement production. Carbon capture and storage (CCS) can be an option to reduce net emissions in these circumstances, although fossil fuel power plants with CCS technology have not yet proven economical.

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

See also: Energy policy

Governments 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. Policies implemented by governments have included national and regional targets to reduce emissions, promoting energy efficiency, 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 (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.

Due to the COVID-19 pandemic, there was a significant reduction in CO₂ emissions globally in 2020.

Projections

See also: Carbon budget

This section is an excerpt from Climate change scenario.[edit]

A climate change scenario is a hypothetical future based on a "set of key driving forces". Scenarios explore the long-term effectiveness of mitigation and adaptation. Scenarios help to understand what the future may hold. They can show which decisions will have the most meaningful effects on mitigation and adaptation.

Closely related to climate change scenarios are pathways, which are more concrete and action-oriented. However, in the literature, the terms scenarios and pathways are often used in a way that they mean the same thing.

Many parameters influence climate change scenarios. Three important parameters are the number of people (and population growth), their economic activity new technologies. Economic and energy models, such as World3 and POLES, quantify the effects of these parameters.

Climate change scenarios exist at a national, regional or global scale. Countries use scenario studies in order to better understand their decisions. This is useful when they are developing their adaptation plans or Nationally Determined Contributions. International goals for mitigating climate change like the Paris Agreement are based on studying these scenarios. For example, the IPCC Special Report on Global Warming of 1.5 °C was a "key scientific input" into the 2018 United Nations Climate Change Conference. Various pathways are considered in the report, describing scenarios for mitigation of global warming. Pathways include for example portfolios for energy supply and carbon dioxide removal.

See also

• Attribution of recent climate change
• Carbon accounting
• Carbon credit
• Carbon Dioxide Information Analysis Center
• Carbon offset
• Carbon tax
• Green hydrogen
• List of countries by renewable electricity production
• Low-carbon economy
• Orbiting Carbon Observatory 2
• Paris Agreement
• Perfluorotributylamine
• Vehicle emission standard
• World energy supply and consumption
• Zero-emissions vehicle

References

Works cited

• Edenhofer, Ottmar; Pichs-Madruga, Ramón; Sokona, Youba; Minx, Jan C.; Farahani, Ellie; Kadner, Susanne; Seyboth, Kristin; et al., eds. (2014). Climate Change 2014 Mitigation of Climate Change: Working Group III Contribution to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (PDF). Cambridge, United Kingdom and New York, NY, USA: Cambridge University Press. ISBN 978-1-107-05821-7 – via IPCC.
• Food security and climate change: The High Level Panel of Experts on Food Security and Nutrition (PDF). Rome: Committee on World Food Security. June 2012.
• Friedlingstein, Pierre; O'Sullivan, Michael; Jones, Matthew W.; Andrew, Robbie M.; Hauck, Judith; Olsen, Are; Peters, Glen P.; Peters, Wouter; Pongratz, Julia; Sitch, Stephen; Le Quéré, Corinne; Canadell, Josep G.; Ciais, Philippe; Jackson, Robert B.; Alin, Simone (11 December 2020). "Global Carbon Budget 2020". Earth System Science Data. 12 (4): 3269–3340. doi:10.5194/essd-12-3269-2020.{{cite journal}}: CS1 maint: unflagged free DOI (link)
• Olivier, J.G.J.; Peters, J.A.H.W. (2020). Trends in global CO₂ and total greenhouse gas emissions (2020) (PDF) (Report). The Hague: PBL Netherlands Environmental Assessment Agency.

External links

• The official greenhouse gas emissions data of developed countries from the UNFCCC
• Annual Greenhouse Gas Index (AGGI) from NOAA
• NOAA CMDL CCGG – Interactive Atmospheric Data Visualization NOAA CO₂ data
• IPCC Website
  • Official IPCC Sixth Assessment Report website