Greenhouse gases là gì

Total U.S. Emissions in 2019 = 6,558 Million Metric Tons of CO2 equivalent (excludes land sector). Percentages may not add up to lớn 100% due to lớn independent rounding.Larger image khổng lồ save or printGases that trap heat in the atmosphere are called greenhouse gases. This section provides information on emissions and removals of the main greenhouse gases to và from the atmosphere. For more information on the other climate forcers, such as black 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 oto is likely to lớn 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 & 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 GWPhường takes into lớn tài khoản the fact that many gases are more effective at warming Earth than CO2, per unit mass.

The GWP.. 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). Exit

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 to lớn higher concentrations in the atmosphere. Greenhouse gas concentrations are measured in parts per million, parts per billion, and even parts per trillion. One part per million is equivalent to one drop of water diluted into 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 vì chưng they stay in the atmosphere?

Each of these gases can remain in the atmosphere for different amounts of time, ranging from a few years to lớn thousands of years. All of these gases remain in the atmosphere long enough to lớn 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 do they impact the atmosphere?

Some gases are more effective sầu than others at making the planet warmer and "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, and how strongly it absorbs energy. Gases with a higher GWP absorb more energy, per pound, than gases with a lower GWPhường, & thus contribute more lớn warming Earth.

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

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Carbon Dioxide Emissions

Properties of Carbon Dioxide

Chemical Formula: CO2Lifetime in Atmosphere: See below1Global Warming Potential (100-year): 1

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 aao ước the atmosphere, oceans, soil, plants, and 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 and soils, to remove sầu và 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

Note: All emission estimates from the Inventory of U.S. Greenhouse Gas Emissions và Sinks: 1990–2019 (excludes lvà sector).Larger image to save or printThe main human activity that emits CO2 is the combustion of fossil fuels (coal, natural gas, và oil) for energy and transportation, although certain industrial processes and 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 among mỏi the atmosphere, ocean, and l& surface as it is both produced và absorbed by many microorganisms, plants, & animals. However, emissions and removal of CO2 by these natural processes tkết thúc to balance, absent anthropogenic impacts. Since the Industrial Revolution began around 1750, human activities have contributed substantially lớn climate change by adding CO2 and other heat-trapping gases to 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 offphối is about 12 percent of total emissions in 2019 & is discussed in more detail in the Lvà Use, Land-Use Change, và Forestry section.

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

Emissions & Trends

Carbon dioxide emissions in the United States increased by about 3 percent between 1990 & 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 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 & short-term factors, including population growth, economic growth, changing energy prices, new technologies, changing behavior, and seasonal temperatures. Between 1990 & 2019, the increase in CO2 emissions corresponded with increased energy use by an expanding economy & population, including overall growth in emissions from increased demand for travel.

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

Reducing Carbon Dioxide Emissions

The most effective way to reduce CO2 emissions is khổng lồ reduce fossil fuel consumption. Many strategies for reducing CO2 emissions from energy are cross-cutting & apply to lớn homes, businesses, industry, and transportation. 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, & using more efficient electrical appliances are all ways to lớn reduce energy use, và thus CO2 emissions.

Energy Conservation

Reducing personal energy use by turning off lights & electronics when not in use reduces electriđô thị demand. Reducing distance traveled in vehicles reduces petroleum consumption. Both are ways to lớn reduce energy CO2 emissions through conservation.

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

Fuel Switching

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

Carbon Capture & Sequestration (CCS)

Carbon dioxide capture and sequestration is a phối of technologies that can potentially greatly reduce CO2 emissions from new and existing coal- and gas-fired power plants, industrial processes, và 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, & injecting the CO2 deep underground at a carefully selected và suitable subsurface geologic formation, such as a nearby abandoned oil field, where it is securely stored.

Learn more about CCS.

Changes in Uses of L& và L& Management Practices

Learn more about Lvà Use, Land Use Change và Forestry Sector.

1 Atmospheric CO2 is part of the global carbon cycle, và 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 lớn ocean sediments.

2IPCC (2013). Climate Change 2013: The Physical Science Basis. Exit Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change.

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. Cambridge University Press, Cambridge, United Kingdom and Thủ đô New York, NY, USA, 1585 pp.

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