User:MurrayScience/Anthropogenic greenhouse gases

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A greenhouse gas (sometimes abbreviated GHG) is a gas that absorbs and emits radiant energy within the thermal infrared range. Greenhouse gases cause the greenhouse effect on planets. The primary greenhouse gases in Earth's atmosphere are water vapor, carbon dioxide , methane , nitrous oxide , and ozone. Without greenhouse gases, the average temperature of Earth's surface would be about -18 °C, rather than the present average of 15 °C. The atmospheres of Venus, Mars and Titan also contain greenhouse gases.

Human activities since the beginning of the Industrial Revolution (around 1750) have produced a 45% increase in the atmospheric concentration of carbon dioxide, from 280 ppm in 1750 to 415 ppm in 2019. The last time the atmospheric concentration of carbon dioxide was this high was over 3 million years ago. This increase has occurred despite the uptake of more than half of the emissions by various natural "sinks" involved in the carbon cycle. The vast majority of anthropogenic carbon dioxide emissions come from combustion of fossil fuels, principally coal, oil, and natural gas, with additional contributions coming from deforestation, changes in land use, soil erosion and agriculture (including livestock). The leading source of anthropogenic methane emissions is animal agriculture, followed by fugitive emissions from gas, oil, coal and other industry, solid waste, wastewater and rice production. Traditional rice cultivation is the second biggest agricultural source of GHG after livestock. Traditional rice production globally accounts for about 1.5% of greenhouse gas emissions, equivalent to all aviation emissions. Its source is methane, created by organic matter decomposing underwater in flooded paddies.

At current emission rates, temperatures could increase by 2 °C (3.6°F), which the United Nations' Intergovernmental Panel on Climate Change (IPCC) designated as the upper limit to avoid "dangerous" levels, by 2036.

Anthropogenic greenhouse gases
Since the beginning of the industrial era, human-caused emissions of carbon dioxide, methane, and nitrous oxide have significantly increased the concentrations of these greenhouse gases in the atmosphere. Although natural sources of carbon dioxide are more than 20 times greater than anthropogenic sources, natural sources are closely balanced by carbon sinks, (mainly photosynthesis by plants and marine plankton). Multiple studies have observed a direct linear relationship between the cumulative amount of emitted by human activity and the increase in global average surface temperatures relative to pre-industrial levels. This phenomenon is known as global warming and has a range of environmental impacts including sea level rise, more intense weather extremes, biodiversity loss, and regional impacts to agricultural productivity.

The major anthropogenic greenhouse gases are carbon dioxide, methane, nitrous oxide and three groups of fluorinated gases (F-gases): sulfur hexafluoride, hydrofluorocarbons (HFCs), and perfluorocarbons (PFCs). In 2005, the Kyoto Protocol implemented commitments among nation states in the United Nations Environment Programme to reduce emissions of these greenhouse gases in order to reduce the onset of global warming. CFCs and hydrofluorocarbons (HFCs) are also greenhouse gases, but are regulated by the Montreal Protocol due to their contribution to ozone depletion.

Experts have identified the need for human civilization to cease emissions of greenhouse gases in order to stop the rise in global temperature. As of 2020, global average surface temperatures have risen approximately 1.0°C relative to the pre-industrial average. The I.P.C.C. has outlined the goal of limiting the global average temperature rise to 1.5°C. In order to accomplish this, global net emissions of methane would need to decrease to near-zero and carbon dioxide to zero by the year 2050. However, emissions of these greenhouse gases have only increased over past decades, about 30% of emissions are from industrial activities or products that have no readily non-emitting alternative, and some have questioned the feasibility of large-scale carbon capture and storage.

Greenhouse gases emissions by sector


Global greenhouse gas (GHG) emissions can be attributed to various sectors of the industrial economy, and can be broadly classified into energy and non-energy related emissions. Energy-related emissions are about two-thirds and primarily result from the combustion of fossil fuel hydrocarbons to generate useable light and heat energy for electricity, heating, industrial processes, and transportation. In 2018, fossil fuels made up 84% of human primary energy sources, which was a decrease from the amount thirty years prior (87%). Non-energy related emissions are about one-third and primarily result from land use, including deforestation, which emits carbon dioxide, livestock, which emit methane through enteric fermentation; rice cultivation, which emits methane; synthetic (inorganic) and manure (organic) fertilizer decomposition, which emits nitrous oxide. A large source of non-energy emissions are from the chemical reactions to make basic materials, generally referred to as industrial processes. These primarily include the -emitting chemical reactions for producing pig iron (an intermediary in the production of steel), aluminum, cement, and ammonia (an intermediary in the production of fertilizer). Other non-energy emissions include fugitive gas, coal mining seam gas, landfill gas, and wastewater emissions.

(Fix links to industrial processes)



Industrial processes
Certain chemical process yield important basic materials for society, e.g., (cement, steel, aluminum, and fertilizer). However, these chemical reactions contribute to climate change by emitting carbon dioxide, a greenhouse gas, through chemical reactions, as well as through the combustion of fossil fuels that generate the high temperatures required.

Cement

 * Calcination – combustion of limestone to remove the carbon in its calcium carbonate (CaCO3), resulting in useable calcium oxide (CaO) (also known as quicklime) and releasing carbon dioxide . Most prominently used to produce cement, although additionally used to provide a chemical flux, as in a blast furnace in the production of pig iron.

Steel

 * Smelting – using carbon monoxide (CO) generally from combusted coke (a fossil fuel) in a blast furnace to remove oxygen from ores, producing pure metal and releasing . Most prominently used in the production of steel.

Aluminum

 * Hall–Héroult process – smelting aluminum (Al2O3) from coke (C) through electrolysis at high temperatures to yield pure aluminum (Al) and a mixture of carbon monoxide (CO) and.

Fertilizer

 * Haber process – separating atmospheric Nitrogen (N2) to make ammonia (NH3), which is used to make nitrogen fertilizer. Often requiring a fossil fuel carbon source to provide the carbon monoxide in a water-gas shift reaction, producing useable hydrogen (H2) and releasing.

Aviation
Something

Electricity

 * Air conditioning

Heating

 * Dryers
 * Stoves

Waste
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) account for up to one third of total anthropogenic 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 concentrations.

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



Greenhouse gases 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 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 categorised 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.

Electricity generation
Electricity generation emits over a quarter of global greenhouse gases. Coal-fired power stations are the single largest emitter, with over 10 Gt in 2018. Although much less polluting than coal plants, natural gas-fired power plants are also major emitters.

Tourism
According to UNEP, global tourism is closely linked to climate change. Tourism is a significant contributor to the increasing concentrations of greenhouse gases in the atmosphere. Tourism accounts for about 50% of traffic movements. Rapidly expanding air traffic contributes about 2.5% of the production of. The number of international travelers is expected to increase from 594 million in 1996 to 1.6 billion by 2020, adding greatly to the problem unless steps are taken to reduce emissions.

Trucking and haulage
The trucking and haulage industry plays a part in production of, contributing around 20% of the UK's total carbon emissions a year, with only the energy industry having a larger impact at around 39%. Average carbon emissions within the haulage industry are falling—in the thirty-year period from 1977 to 2007, the carbon emissions associated with a 200-mile journey fell by 21 percent; NOx emissions are also down 87 percent, whereas journey times have fallen by around a third.

Plastic
Plastic is produced mainly from fossil fuels. Plastic manufacturing is estimated to use 8 percent of yearly global oil production. 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.

From the other side, if it is placed in a landfill, it becomes a carbon sink although biodegradable plastics have caused methane emissions. 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.

Pharmaceutical industry
The pharmaceutical industry emitted 52 megatonnes of carbon dioxide into the atmosphere in 2015. This is more than the automotive sector. However this analysis used the combined emissions of conglomerates which produce pharmaceuticals as well as other products.

Regional and national attribution of emissions
According to the Environmental Protection Agency (EPA), GHG emissions in the United States can be traced from different sectors.

There are several ways of measuring greenhouse gas emissions, for example, see World Bank (2010) for tables of national emissions data. 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 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: Contribution of a 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.
 * What sectors are included in the calculation (e.g., energy industries, industrial processes, agriculture etc.): There is often a conflict between transparency and availability of data.
 * 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.

These measures are sometimes used by countries to assert various policy/ethical positions on climate change (Banuri et al., 1996, p. 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 measured over long time periods. This measurement type is called historical or cumulative emissions. Cumulative emissions give some indication of who is responsible for the build-up in the atmospheric concentration of greenhouse gases (IEA, 2007, p. 199).

The national accounts balance would be positively related to carbon emissions. The national accounts balance shows the difference between exports and imports. For many richer nations, such as the United States, the accounts balance is negative because more goods are imported than they are exported. This is mostly due to the fact that it is cheaper to produce goods outside of developed countries, leading the economies of developed countries to become increasingly dependent on services and not goods. We believed that a positive accounts balance would means that more production was occurring in a country, so more factories working would increase carbon emission levels.

Emissions may also be measured across shorter time periods. Emissions changes may, for example, be measured against a 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 (Banuri et al., 1996, pp. 106–07).

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.

From 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 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 (Banuri et al., 1996, pp. 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 (Banuri et al., 1996, p. 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
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) (Banuri et al., 1996, p. 96). Calculations based on MER show large differences in intensities between developed and developing countries, whereas calculations based on PPP show smaller differences.

Cumulative and historical emissions
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. 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. The estimate of total emissions includes biotic carbon emissions, mainly from deforestation. Banuri et al. (1996, p. 94) 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.

Including biotic emissions brings about the same controversy mentioned earlier regarding carbon sinks and land-use change (Banuri et al., 1996, pp. 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.

Non-OECD 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%; Russia, 11%; China, 9%; other OECD countries, 5%; Japan, 4%; India, 3%; and the rest of the world, 18%.

Changes since a particular base year
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. 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).

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, Iran, and Australia (which apart from the oil rich Persian Gulf states, now has the highest percapita 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 the 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.

Annual
In 2009, the annual top ten emitting countries accounted for about two-thirds of the world's annual energy-related 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  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). 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.

Effect of 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. Analysis by the UNFCCC (2011) 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.

Projections
A wide range of projections of future emissions have been produced. Rogner et al. (2007) assessed the scientific literature on greenhouse gas projections. Rogner et al. (2007) concluded that unless energy policies changed substantially, the world would 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.

Relative 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).

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