Greenhouse gas emissions are greenhouse gases vented to the Earth's atmosphere because of humans: the greenhouse effect of their 50 billion tons a year causes climate change. Most is carbon dioxide from burning fossil fuels: coal, oil and natural gas. The largest polluters 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%.
Electricity generation and transport are large emitters. 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.
Carbon dioxide, methane, nitrous oxide and three groups of fluorinated gases (sulfur hexafluoride , hydrofluorocarbons (HFCs), and perfluorocarbons (PFCs)) are the major anthropogenic greenhouse gases, and are regulated under the Paris Agreement.:147
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 often are 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:
These measures are sometimes used by countries to assert various policy/ethical positions on climate change.:94 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.:199
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).:146, 149 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.:370 Per capita emissions may be based on historical or annual emissions.:106-107
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.
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. As a result of this balance, the atmospheric mole fraction of carbon dioxide remained between 260 and 280 parts per million for the 10,000 years between the end of the last glacial maximum and the start of the industrial era. 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 main sources of greenhouse gases due to human activity are:
The seven sources of from fossil fuel combustion are (with percentage contributions for 2000-2004):
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.
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.
|Food Types||Greenhouse Gas Emissions (g CO2-Ceq per g protein)|
Approximately 3.5% of the overall human impact 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.
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 digital sector produces between 2% and 4% of global GHG emissions. However the sector reduces emissions from other sectors which have a larger global share, such as transport of people, and possibly buildings and industry.
Steel and aluminium 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."
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 while over 25% in 2018.
Plastic is produced mainly from fossil fuels. Plastics are estimated to emit between 1% and 2% of global GhG over their lifecycle. 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 plastic will contribute greenhouse gases in the equivalent of 850 million tonnes of carbon dioxide (CO2) to the atmosphere in 2019. In current trend, annual emissions will grow to 1.34 billion tonnes by 2030. By 2050 plastic could emit 56 billion tonnes of Greenhouse gas emissions, 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.
Wastewater as well as sanitation systems are known to contribute to greenhouse-gas emissions (GHG)[quantify] 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,[when?] attention to adaptation needs within the sanitation sector is just beginning to gain momentum.
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.
|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|
|Concentrated solar power||8.8||27||63|
|Ocean (Tidal and wave)||5.6||17||28|
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).
|Liquefied petroleum gas||139||59.76||215.14|
|Tires/tire derived fuel||189||81.26||292.54|
|Wood and wood waste||195||83.83||301.79|
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.:92-93
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.:93 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 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).:96 Calculations based on MER show large differences in intensities between developed and developing countries, whereas calculations based on PPP show smaller differences.
Cumulative anthropogenic (i.e., human-emitted) emissions of 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,:15 calculated per capita cumulative emissions based on then-current population. 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 emissions between 1890 and 2007.:179-80 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%.:179-80
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.
Estimates of total emissions do include biotic carbon emissions, mainly from deforestation.:94 Including biotic emissions brings about the same controversy mentioned earlier regarding carbon sinks and land-use change.:93-94 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.
Between 1970 and 2004, global growth in annual emissions was driven by North America, Asia, and the Middle East. 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 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.:17-18 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.:17-18 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).
Annual per capita emissions in the industrialized countries are typically as much as ten times the average in developing countries.:144 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. For China's annual emissions in 2008, the Netherlands Environmental Assessment Agency estimated an uncertainty range of about 10%.
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.
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.
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.:179:1 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):4 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. Based on annual emissions data from the year 2004, and on a per-capita consumption basis, the top-5 emitting countries were found to be (in t per person, per year): Luxembourg (34.7), the US (22.0), Singapore (20.2), Australia (16.7), and Canada (16.6).:5 [needs update]Carbon Trust research revealed that approximately 25% of all emissions from human activities 'flow' (i.e., are imported or exported) from one country to another. Major developed economies were found to be typically net importers of embodied carbon emissions--with UK consumption emissions 34% higher than production emissions, and Germany (29%), Japan (19%) and the US (13%) also significant net importers of embodied emissions.[needs update]
This section needs to be updated.(December 2019)
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.:3 Analysis by the UNFCCC (2011):8 suggested that policies and measures undertaken by Annex I Parties may have produced emission savings of 1.5 thousand Tg -eq in the year 2010, with most savings made in the energy sector. The projected emissions saving of 1.5 thousand Tg -eq is measured against a hypothetical "baseline" of Annex I emissions, i.e., projected Annex I emissions in the absence of policies and measures. The total projected Annex I saving of 1.5 thousand -eq does not include emissions savings in seven of the Annex I Parties.:8
Due to the COVID-19 pandemic, there was a significant reduction in emissions globally in 2020.
This section needs to be updated.(December 2019)
A wide range of projections of future emissions have been produced. Unless energy policies change substantially, the world will continue to depend on fossil fuels until 2025-2030. Projections suggest that more than 80% of the world's energy will come from fossil fuels. This conclusion was based on "much evidence" and "high agreement" in the literature. Projected annual energy-related emissions in 2030 were 40-110% higher than in 2000, with two-thirds of the increase originating in developing countries. Projected annual per capita emissions in developed country regions remained substantially lower (2.8-5.1 tonnes ) than those in developed country regions (9.6-15.1 tonnes ). Projections consistently showed increase in annual world emissions of "Kyoto" gases, measured in -equivalent) of 25-90% by 2030, compared to 2000.
The burning of coal, natural gas, and oil for electricity and heat is the largest single source of global greenhouse gas emissions.
... According to the EPA, approximately one ounce of carbon dioxide is emitted for each ounce of polyethylene (PET) produced. PET is the type of plastic most commonly used for beverage bottles. ...'