Total U.S. Emissions in 2019 = 6,558 Million Metric Tons of CO2 equivalent (excludes l& sector). Percentages may not add up lớn 100% due khổng lồ independent rounding.Larger image khổng lồ save or print Gases that trap heat in the atmosphere are called greenhouse gases. This section provides information on emissions & removals of the main greenhouse gases khổng lồ và from the atmosphere. For more information on the other climate forcers, such as blachồng carbon, please visit the Climate Change Indicators: Climate Forcing page.

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6,457 million metric tons of CO2: What does that mean?

An explanation of units:

A million metric tons is equal lớn about 2.2 billion pounds, or 1 trillion grams. For comparison, a small car is likely to weigh a little more than 1 metric ton. Thus, a million metric tons is roughly the same mass as 1 million small cars!

The U.S. Inventory uses metric units for consistency and comparability with other countries. For reference, a metric ton is a little bit larger (about 10%) than a U.S. "short" ton.

GHG emissions are often measured in carbon dioxide (CO2) equivalent. To convert emissions of a gas into CO2 equivalent, its emissions are multiplied by the gas"s Global Warming Potential (GWP). The GWP takes into tài khoản the fact that many gases are more effective sầu at warming Earth than CO2, per unit mass.

The GWPhường. values appearing in the Emissions webpages reflect the values used in the U.S. Inventory, which are drawn from the IPCC’s Fourth Assessment Report (AR4). For further discussion of GWPs & an estimate of GHG emissions using updated GWPs, see Annex 6 of the U.S. Inventory và the IPCC"s discussion on GWPs (PDF)(106 pp, 7.7MB).


Each gas"s effect on climate change depends on three main factors:

How much is in the atmosphere?

Concentration, or abundance, is the amount of a particular gas in the air. Larger emissions of greenhouse gases lead lớn higher concentrations in the atmosphere. Greenhouse gas concentrations are measured in parts per million, parts per billion, và even parts per trillion. One part per million is equivalent lớn one drop of water diluted inlớn about 13 gallons of liquid (roughly the fuel tank of a compact car). To learn more about the increasing concentrations of greenhouse gases in the atmosphere, visit the Climate Change Indicators: Atmospheric Concentrations of Greenhouse Gases page.

How long vị they stay in the atmosphere?

Each of these gases can remain in the atmosphere for different amounts of time, ranging from a few years khổng lồ thousands of years. All of these gases remain in the atmosphere long enough khổng lồ become well mixed, meaning that the amount that is measured in the atmosphere is roughly the same all over the world, regardless of the source of the emissions.

How strongly vị they impact the atmosphere?

Some gases are more effective sầu than others at making the planet warmer và "thickening the Earth"s blanket."

For each greenhouse gas, a Global Warming Potential (GWP) has been calculated lớn reflect how long it remains in the atmosphere, on average, và how strongly it absorbs energy. Gases with a higher GWP absorb more energy, per pound, than gases with a lower GWP., and thus contribute more to warming Earth.

Note: All emission estimates are from the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990–2019.


Carbon Dioxide Emissions


Properties of Carbon Dioxide

Carbon dioxide (CO2) is the primary greenhouse gas emitted through human activities. In 2019, CO2 accounted for about 80 percent of all U.S. greenhouse gas emissions from human activities. Carbon dioxide is naturally present in the atmosphere as part of the Earth"s carbon cycle (the natural circulation of carbon among muốn the atmosphere, oceans, soil, plants, và animals). Human activities are altering the carbon cycle–both by adding more CO2 to lớn the atmosphere, & by influencing the ability of natural sinks, lượt thích forests & soils, lớn remove & store CO2 from the atmosphere. While CO2 emissions come from a variety of natural sources, human-related emissions are responsible for the increase that has occurred in the atmosphere since the industrial revolution.2


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Note: All emission estimates from the Inventory of U.S. Greenhouse Gas Emissions & Sinks: 1990–2019 (excludes l& sector).Larger image to lớn save or print The main human activity that emits CO2 is the combustion of fossil fuels (coal, natural gas, and oil) for energy and transportation, although certain industrial processes và land-use changes also emit CO2. The main sources of CO2 emissions in the United States are described below.

Carbon dioxide is constantly being exchanged ahy vọng the atmosphere, ocean, và l& surface as it is both produced & absorbed by many microorganisms, plants, and animals. However, emissions and removal of CO2 by these natural processes tend khổng lồ balance, absent anthropogenic impacts. Since the Industrial Revolution began around 1750, human activities have contributed substantially to lớn climate change by adding CO2 and other heat-trapping gases lớn the atmosphere.

In the United States, since 1990, the management of forests & other land (e.g., cropl&, grasslands, etc.) has acted as a net sink of CO2, which means that more CO2 is removed from the atmosphere, và stored in plants and trees, than is emitted. This carbon sink offmix is about 12 percent of total emissions in 2019 and is discussed in more detail in the L& Use, Land-Use Change, & Forestry section.

To find out more about the role of CO2 in warming the atmosphere và its sources, visit the Climate Change Indicators page.

Emissions & Trends

Carbon dioxide emissions in the United States increased by about 3 percent between 1990 và 2019. Since the combustion of fossil fuel is the largest source of greenhouse gas emissions in the United States, changes in emissions from fossil fuel combustion have sầu historically been the dominant factor affecting total U.S. emission trends. Changes in CO2 emissions from fossil fuel combustion are influenced by many long-term và short-term factors, including population growth, economic growth, changing energy prices, new technologies, changing behavior, and seasonal temperatures. Between 1990 và 2019, the increase in CO2 emissions corresponded with increased energy use by an expanding economy và population, including overall growth in emissions from increased dem& for travel.


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Note: All emission estimates from the Inventory of U.S. Greenhouse Gas Emissions & Sinks: 1990–2019.Larger image lớn save or print

Reducing Carbon Dioxide Emissions

The most effective way to reduce CO2 emissions is to lớn reduce fossil fuel consumption. Many strategies for reducing CO2 emissions from energy are cross-cutting và apply lớn homes, businesses, industry, & transportation.

xemlienminh360.net is taking common sense regulatory actions lớn reduce greenhouse gas emissions.

Examples of Reduction Opportunities for Carbon DioxideStrategyExamples of How Emissions Can be Reduced
Energy Efficiency

Improving the insulation of buildings, traveling in more fuel-efficient vehicles, và using more efficient electrical appliances are all ways lớn reduce energy use, & thus CO2 emissions.

Energy Conservation

Reducing personal energy use by turning off lights and electronics when not in use reduces electrithành phố demvà. Reducing distance traveled in vehicles reduces petroleum consumption. Both are ways lớn reduce energy CO2 emissions through conservation.

Learn more about What You Can Do at Home, at School, in the Office, and on the Road to lớn save energy & reduce your carbon footprint.

Fuel Switching

Producing more energy from renewable sources & using fuels with lower carbon contents are ways khổng lồ reduce carbon emissions.

Carbon Capture and Sequestration (CCS)

Carbon dioxide capture và sequestration is a phối of technologies that can potentially greatly reduce CO2 emissions from new và existing coal- và gas-fired power plants, industrial processes, and other stationary sources of CO2. For example, capturing CO2 from the stacks of a coal-fired power plant before it enters the atmosphere, transporting the CO2 via pipeline, và injecting the CO2 deep underground at a carefully selected and suitable subsurface geoxúc tích formation, such as a nearby abandoned oil field, where it is securely stored.

Learn more about CCS.

Changes in Uses of Lvà & L& Management Practices

Learn more about Land Use, L& Use Change & Forestry Sector.

1 Atmospheric CO2 is part of the global carbon cycle, and therefore its fate is a complex function of geochemical & biological processes. Some of the excess carbon dioxide will be absorbed quickly (for example, by the ocean surface), but some will remain in the atmosphere for thousands of years, due in part to lớn the very slow process by which carbon is transferred to lớn ocean sediments.

2IPCC (2013). Climate Change 2013: The Physical Science Basis.Contribution of Working Group I to lớn the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. . Cambridge University Press, Cambridge, United Kingdom và Thủ đô New York, NY, USA, 1585 pp.


In 2019, methane (CH4) accounted for about 10 percent of all U.S. greenhouse gas emissions from human activities. Human activities emitting methane include leaks from natural gas systems and the raising of livestochồng. Methane is also emitted by natural sources such as natural wetlands. In addition, natural processes in soil and chemical reactions in the atmosphere help remove CH4 from the atmosphere. Methane"s lifetime in the atmosphere is much shorter than carbon dioxide (CO2), but CH4 is more efficient at trapping radiation than CO2. Pound for pound, the comparative sầu impact of CH4 is 25 times greater than CO2 over a 100-year period.1

Globally, 50-65 percent of total CH4 emissions come from human activities.2, 3 Methane is emitted from energy, industry, agriculture, land use, và waste management activities, described below.


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Methane is also emitted from a number of natural sources. Natural wetlands are the largest source, emitting CH4 from bacteria that decompose organic materials in the absence of oxyren. Smaller sources include termites, oceans, sediments, volcanoes, & wildfires.

To find out more about the role of CH4 in warming the atmosphere and its sources, visit the Climate Change Indicators page.

Emissions & Trends

Methane emissions in the United States decreased by 15 percent between 1990 & 2019. During this time period, emissions increased from sources associated with agricultural activities, while emissions decreased from sources associated with landfills, coal mining, và from natural gas và petroleum systems.


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Note: All emission estimates from the Inventory of U.S. Greenhouse Gas Emissions và Sinks: 1990-2019 . These estimates use a global warming potential for methane of 25, based on reporting requirements under the United Nations Framework Convention on Climate Change.Larger image to save or print

Reducing Methane Emissions

There are a number of ways to reduce CH4 emissions. Some examples are discussed below. xemlienminh360.net has a series of voluntary programs for reducing CH4 emissions, in addition khổng lồ regulatory initiatives. xemlienminh360.net also supports the Global Methane Initiative sầu, an international partnership encouraging global methane reduction strategies.

Examples of Reduction Opportunities for MethaneEmissions SourceHow Emissions Can be Reduced
Industry

Upgrading the equipment used khổng lồ produce, store, & transport oil và natural gas can reduce many of the leaks that contribute khổng lồ CH4 emissions. Methane from coal mines can also be captured and used for energy. Learn more about the xemlienminh360.net"s Natural Gas STAR Program & Coalbed Methane Outreach Program.

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Agriculture

Methane from manure management practices can be reduced và captured by altering manure management strategies. Additionally, modifications to animal feeding practices may reduce emissions from enteric fermentation. Learn more about improved manure management practices at xemlienminh360.net"s AgSTAR Program.

Waste from Homes và Businesses

Because CH4 emissions from landfill gas are a major source of CH4 emissions in the United States, emission controls that capture landfill CH4 are an effective sầu reduction strategy. Learn more about these opportunities & the xemlienminh360.net"s Landfill Methane Outreach Program.

References

1IPCC (2007). Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to lớn the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. . Cambridge University Press. Cambridge, United Kingdom 996 pp.2IPCC (2013). Climate Change 2013: The Physical Science Basis.Contribution of Working Group I to lớn the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. . Cambridge University Press, Cambridge, United Kingdom & Thành Phố New York, NY, USA, 1585 pp.3The Global Carbon Project (2019).


In 2019, nitrous oxide (N2O) accounted for about 7 percent of all U.S. greenhouse gas emissions from human activities. Human activities such as agriculture, fuel combustion, wastewater management, and industrial processes are increasing the amount of N2O in the atmosphere. Nitrous oxide is also naturally present in the atmosphere as part of the Earth"s nitroren cycle, và has a variety of natural sources. Nitrous oxide molecules stay in the atmosphere for an average of 114 years before being removed by a sink or destroyed through chemical reactions. The impact of 1 pound of N2O on warming the atmosphere is almost 300 times that of 1 pound of carbon dioxide.1


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Note: All emission estimates from the Inventory of U.S. Greenhouse Gas Emissions & Sinks: 1990–2019 (excludes l& sector).Larger image lớn save sầu or print Globally, about 40 percent of total N2O emissions come from human activities.2 Nitrous oxide is emitted from agriculture, l& use, transportation, industry, and other activities, described below.

Nitrous oxide emissions occur naturally through many sources associated with the nitrogen cycle, which is the natural circulation of nitrogene aước ao the atmosphere, plants, animals, and microorganisms that live sầu in soil and water. Nitrogene takes on a variety of chemical forms throughout the nitroren cycle, including N2O. Natural emissions of N2O are mainly from bacteria breaking down nitrogene in soils and the oceans. Nitrous oxide is removed from the atmosphere when it is absorbed by certain types of bacteria or destroyed by ultraviolet radiation or chemical reactions.

To find out more about the sources of N2O & its role in warming the atmosphere, visit the Climate Change Indicators page.

Emissions và Trends

Nitrous oxide emissions in the United States have sầu remained relatively flat between 1990 & 2019. Nitrous oxide emissions from điện thoại combustion decreased by 60 percent from 1990 khổng lồ 2019 as a result of emission control standards for on-road vehicles. Nitrous oxide emissions from agricultural soils have varied during this period và were about 9 percent higher in 2019 than in 1990, primarily driven by increasing use of nitrogen fertilizers.


Note: All emission estimates from the Inventory of U.S. Greenhouse Gas Emissions & Sinks: 1990–2019.Larger image khổng lồ save sầu or print

Reducing Nitrous Oxide Emissions

There are a number of ways to lớn reduce emissions of N2O, discussed below.

Examples of Reduction Opportunities for Nitrous Oxide EmissionsEmissions SourceExamples of How Emissions Can be Reduced
Agriculture

The application of nitrogene fertilizers accounts for the majority of N2O emissions in the United States. Emissions can be reduced by reducing nitrogen-based fertilizer applications & applying these fertilizers more efficiently,3 as well as modifying a farm"s manure management practices.

Fuel CombustionNitrous oxide is a bysản phẩm of fuel combustion, so reducing fuel consumption in motor vehicles và secondary sources can reduce emissions.

Additionally, the introduction of pollution control technologies (e.g., catalytic converters to reduce exhaust pollutants from passenger cars) can also reduce emissions of N2O.

IndustryNitrous oxide is generally emitted from industry through fossil fuel combustion, so technological upgrades and fuel switching are effective sầu ways to lớn reduce industry emissions of N2O.

Production of adipic acid results in N2O emissions that can be reduced through technological upgrades.

References

1 IPCC (2007) Climate Change 2007: The Physical Science Basis. Contribution of Working Group I khổng lồ the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. . Cambridge University Press. Cambridge, United Kingdom 996 pp.2IPCC (2013). Climate Change 2013: The Physical Science Basis. Contribution of Working Group I lớn the Fifth Assessment Report of the Intergovernmental Panel on Climate Change. . Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 1585 pp.3xemlienminh360.net (2005). Greenhouse Gas Mitigation Potential in U.S. Forestry và Agriculture. U.S. Environmental Protection Agency, Washington, DC, USA.


Unlượt thích many other greenhouse gases, fluorinated gases have sầu no natural sources and only come from human-related activities. They are emitted through their use as substitutes for ozone-depleting substances (e.g., as refrigerants) và through a variety of industrial processes such as aluminum and semiconductor manufacturing. Many fluorinated gases have sầu very high global warming potentials (GWPs) relative sầu to other greenhouse gases, so small atmospheric concentrations can have sầu disproportionately large effects on global temperatures. They can also have long atmospheric lifetimes—in some cases, lasting thousands of years. Like other long-lived greenhouse gases, most fluorinated gases are well-mixed in the atmosphere, spreading around the world after they are emitted. Many fluorinated gases are removed from the atmosphere only when they are destroyed by sunlight in the far upper atmosphere. In general, fluorinated gases are the most potent and longest lasting type of greenhouse gases emitted by human activities.

There are four main categories of fluorinated gases—hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), sulfur hexafluoride (SF6), & nitroren trifluoride (NF3). The largest sources of fluorinated gas emissions are described below.


Industry. Perfluorocarbons are produced as a byproduct of aluminum production and are used in the manufacturing of semiconductors. PFCs generally have long atmospheric lifetimes and GWPs near 10,000. Sulfur hexafluoride is used in magnesium processing và semiconductor manufacturing, as well as a tracer gas for leak detection. HFC-23 is produced as a byproduct of HCFC-22 production và is used in semiconductor manufacturing.Transmission và Distribution of Electricity. Sulfur hexafluoride is used as an insulating gas in electrical transmission equipment, including circuit breakers. The GWPhường of SF6 is 22,800, making it the most potent greenhouse gas that the Intergovernmental Panel on Climate Change has evaluated.

To find out more about the role of fluorinated gases in warming the atmosphere and their sources, visit the Fluorinated Greenhouse Gas Emissions page.

Emissions & Trends

Overall, fluorinated gas emissions in the United States have sầu increased by about 86 percent between 1990 and 2019. This increase has been driven by a 275 percent increase in emissions of hydrofluorocarbons (HFCs) since 1990, as they have sầu been widely used as a substitute for ozone-depleting substances. Emissions of perfluorocarbons (PFCs) and sulfur hexafluoride (SF6) have actually declined during this time due lớn emission reduction efforts in the aluminum production industry (PFCs) & the electriđô thị transmission and distribution industry (SF6).


Note: All emission estimates from the Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990–2019.Larger image lớn save or print

Reducing Fluorinated Gas Emissions

Because most fluorinated gases have a very long atmospheric lifetime, it will take many years to lớn see a noticeable decline in current concentrations. However, there are a number of ways to lớn reduce emissions of fluorinated gases, described below.

Examples of Reduction Opportunities for Fluorinated GasesEmissions SourceExamples of How Emissions Can be Reduced
Substitution of Ozone-Depleting Substances in Homes and Businesses

Refrigerants used by businesses và residences emit fluorinated gases. Emissions can be reduced by better handling of these gases & use of substitutes with lower global warming potentials & other technological improvements. Visit xemlienminh360.net"s Ozone Layer Protection site lớn learn more about reduction opportunities in this sector.

Industry

Industrial users of fluorinated gases can reduce emissions by adopting fluorinated gas recycling & destruction processes, optimizing production to minimize emissions, và replacing these gases with alternatives. xemlienminh360.net has the following resources lớn manage these gases in the Industry sector:

Electricity Transmission và Distribution

Sulfur hexafluoride is an extremely potent greenhouse gas that is used for several purposes when transmitting electricity through the power grid. xemlienminh360.net is working with industry lớn reduce emissions through the SF6 Emission Reduction Partnership for Electric Power Systems, which promotes leak detection và rxemlienminh360.netir, use of recycling equipment, and employee training.

Transportation

Hydrofluorocarbons (HFCs) are released through the leakage of refrigerants used in vehicle air-conditioning systems. Leakage can be reduced through better system components, và through the use of alternative sầu refrigerants with lower global warming potentials than those presently used. xemlienminh360.net’s light-duty and heavy-duty vehicle standards provided incentives for manufacturers to produce vehicles with lower HFC emissions.

References

1IPCC (2007) Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. . Cambridge University Press. Cambridge, United Kingdom 996 pp.

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