Greenhouse gas emissions

Overview

Greenhouse gas emissionsrefer to the production of gases that may accumulate in Earth’s atmosphere and contribute to the greenhouse effect. The greenhouse effect refers to the process by which Earth receives and stores energy from the sun. The sun constantly emits huge amounts of energy in the forms of visible light, infrared radiation, and ultraviolet radiation. This energy brings life-giving warmth to Earth and triggers Earth’s complex climatic systems. When excessive amounts of greenhouse gases accumulate in the atmosphere, however, they trap more of the sun’s energy than would otherwise be retained.

Holding this energy, rather than letting it escape back into space, causes extra heat to form on Earth. This change in heat and energy levels has a complex and multifaceted effect on the planet, which scientists are still studying. Most scientists believe that the greenhouse effect is causing widespread climate change across the planet. Some of these effects may lead to serious imbalances in natural processes and disasters such as droughts, floods, tropical storms, and dangerously high temperatures.

Many governments, organizations, and concerned citizens are promoting changes to human behavior in hopes of reducing climate change. One of the first and most critical steps is controlling the levels of greenhouse gases in the atmosphere. Reducing human-caused greenhouse gas emissions is a necessary, but extremely difficult, step in this process.

The emission of greenhouse gases may occur due to natural processes, such as decomposition of matter, volcanic eruptions, and natural forest fires. However, natural emissions are usually kept in an overall balance with processes such as the carbon cycle that reuse greenhouse gases, keeping them from lingering in the atmosphere.

Instead, most environmental scientists focus on greenhouse gas emissions caused by human activities, which have greatly increased the amount of these gases in the atmosphere and offset natural balances. Human activities that cause greenhouse gas emissions include the burning of fossil fuels such as oil, coal, and natural gas, and various industrial and agricultural processes. Humans also contribute to an excessive amount of atmospheric greenhouse gases by cutting down plant life that would otherwise help to filter greenhouse gases from the air.

The most common types of greenhouse gases are carbon dioxide, methane, nitrous oxide, and fluorinated gas. The first three occur naturally but are boosted to hazardous levels by human behaviors, while the latter is primarily caused by people. These gases may come from various sources. They may function differently and may exist in the atmosphere for varying timespans. However, they are all known to promote the greenhouse effect and, most scientists believe, potentially dangerous climate change.

After greenhouse gases are emitted, most drift into the atmosphere. They may move and mix with other gases, and some may be drawn away by natural forces. Scientists have attempted to determine how long greenhouse gases can exist in the atmosphere after they are emitted. This helps to determine how dangerous each type of gas is likely to be. The atmospheric lifespan of carbon dioxide, the most plentiful greenhouse gas, is unpredictable. A large quantity of carbon dioxide is necessary for the natural carbon cycle, so it may become engaged in a process lasting many years or even centuries or millennia. Excess carbon dioxide may be absorbed by plants or water relatively quickly, while other molecules may drift into the atmosphere for thousands of years.

Methane, alternately, has a relatively predictable atmospheric lifespan of about twelve years. However, it is a potent gas, so it may have a strong effect in even that relatively short period. Scientists predict that nitrous oxide particles may be able to exist in the atmosphere for 114 years. Meanwhile, the human-made fluorinated gases present a much longer timescale, which is of significant concern to environmental scientists. Hydrofluorocarbons may last as long as 270 years; nitrogen trifluoride may last 740 years; sulfur hexafluoride may last 3,200 years; and perfluorocarbons may be able to exist in Earth’s atmosphere for up to 50,000 years (United States Environmental Protection Agency). These numbers demonstrate how human actions can have a long-term effect on the balance of the atmosphere.

Further Insights

Both natural and human-based activities may emit greenhouse gases. Greenhouse gases are types of gas that can trap heat in the Earth’s atmosphere. Many kinds of gas may be considered greenhouse gas. However, the main greenhouse gases in much of the world are carbon dioxide, methane, and nitrous oxide. These three materials exist in nature and are part of natural cycles, meaning that the environment uses them and the balance of nature accounts for a certain amount of them. However, these gases also result from a variety of human activities. Over time, human activities have caused the levels of these gases to far exceed what occurs naturally, and thus offset the balance of nature in unprecedented ways.

Carbon dioxide, chemically represented as CO2, is by far the most abundant of the greenhouse gases emitted. According to the Environmental Protection Agency (EPA), in the United States carbon dioxide made up 79 percent of greenhouse gas emissions in 2020. Carbon dioxide exists naturally as part of the planet’s carbon cycle, in which carbon moves between the air, the water, the land, and living things. Humans have offset the carbon cycle in two primary ways. One, they have greatly increased the amount of carbon dioxide created, much of which then accumulates in the atmosphere, overwhelming Earth’s ability to process it. Humans have also altered or damaged other aspects of the carbon cycle, mainly by cutting down trees that would otherwise have naturally captured carbon from the air.

Carbon dioxide emissions from human activities primarily comes from burning. When people burn fossil fuels (oil, coal, and natural gas) or wood and other natural materials to use their energy, the process releases carbon dioxide into the atmosphere. In addition, some chemical processes in human industry, such as manufacturing cement, can release additional carbon dioxide. A main contributor in the human production of carbon dioxide is transportation. Gasoline and diesel fuels, both derivatives of oil, release their energy when burned. Burning this fuel in vehicle engines has vastly increased carbon dioxide emissions in the twentieth and twenty-first centuries. Vehicles commonly using oil-based fuels include cars, trucks, motorcycles, aircraft, boats, and trains.

Humans also emit substantial amounts of carbon dioxide when they burn fossil fuels to produce electricity. In this case, the fossil fuel that is most efficient in electricity production is coal, the burning of which releases carbon dioxide and other materials into the atmosphere. Meanwhile, humans may also create unwanted carbon dioxide increases in other ways. Numerous industries rely on chemical reactions that create this greenhouse gas. A few examples include iron and steel production and cement manufacturing.

Methane, chemically represented as CH4, is a lesser, but still highly abundant and impactful, type of greenhouse gas that poses a danger to the environment. Like carbon dioxide, methane is a natural material that is emitted in significant quantities by non-human activities. Animals naturally create methane in their bodies when they digest food. The process of decomposition, including the decomposition of plant and animal life in wetlands, may also create large amounts of methane. These processes have both occurred in nature for far longer than humans have even existed. However, human activity has greatly heightened both.

Raising of huge quantities of livestock for food production has increased methane emission tremendously. So too have human activities such as creating landfills for waste products, whose slow decomposition creates this greenhouse gas. In the twenty-first century, more than half of methane emissions may be traced to human activities. Methane is also the main component in natural gas. When humans mine for natural gas, and capture, store, process, and transport the material, they unavoidably release some into the atmosphere. Other mining and processing activities for fossil fuels may also produce methane. (Methane is also produced during natural processes such as volcanic eruptions and non-human-induced wildfires.)

Nitrous oxide, designated N2O, is a third major form of greenhouse gas. Like carbon dioxide and methane, nitrous oxide may be emitted naturally. The gas is linked to the natural nitrogen cycle. In this cycle, nitrogen constantly circulates between the air and various living things, including plants, animals, and microorganisms. During different stages of this process, nitrogen takes on multiple forms, including that of nitrous oxide. That naturally produced nitrous oxide may contribute to what is already present in the atmosphere.

However, large quantities of nitrous oxide emission occur due to human activities; this has elevated the atmospheric nitrous oxide to potentially dangerous levels that may offset the natural balance. Nitrous oxide created by human activity, which accounts for about 40 percent of nitrous oxide emissions globally, arises from many pursuits, but mainly agriculture. In many countries, farmers produce nitrous oxide during activities such as crop fertilization and the storage, use, and application of manure. Burning leftover agricultural material may also create nitrous oxide. Similarly, people who use fertilizers in other areas, including forests, homes, and recreational areas, may also contribute to this emission.

Industries may produce and emit nitrous oxide while manufacturing many types of products, including fertilizer. The production of adipic acid, which is useful for making synthetic fabric fibers and other products, may also emit nitrous oxide. Humans may also generate nitrous oxide while treating sewage and similar waste materials. Finally, the burning of fossil fuels may cause nitrous oxide to enter the atmosphere, as well as other greenhouse gases including carbon dioxide.

Another major category of greenhouse gas is fluorinated gas. Unlike carbon dioxide, methane, and nitrous oxide, fluorinated gases are very rare or not present in nature, so their emission into the atmosphere may basically be attributable to human activity alone. Some of the most common types of fluorinated gas include hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), nitrogen trifluoride (NF3), and sulfur hexafluoride (SF6). This category of greenhouse gas is less prevalent than carbon dioxide, methane, or nitrous oxide. However, fluorinated gases are unusually strong and may contribute more strongly to the greenhouse effect than an equivalent mass of carbon dioxide. This makes fluorinated gases the subject of much concern.

Hydrofluorocarbons are one of the most abundant forms of fluorinated gas emitted worldwide. Humans developed and used hydrofluorocarbons to replace other gases, chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs), other greenhouse gases which were known to damage Earth’s ozone layer. (Under the Montreal Protocol, many countries have agreed to phase out the use of these gases.) Hydrofluorocarbons have less impact on the ozone layer but still significantly heighten the greenhouse effect.

Most hydrofluorocarbons humans produce are used as refrigerants, meaning they can create coolness. They are commonly used in air conditioning and refrigerators. During the manufacturing, transport, and disposal of these cooling appliances, some of the gases may leak out into the atmosphere, contributing to the greenhouse gas problem. Many people also use hydrofluorocarbons as aerosol propellants, or the gas that ejects paint or hairspray from aerosol cans, or as fire retardants. These uses are responsible for the majority of fluorinated gas emissions. However, some other sources of this potent greenhouse gas include the aluminum production industry and the creation of electrical equipment such as circuit breakers.

Discourse

Most major types of greenhouse gas exist in nature and have been present in Earth’s atmosphere for millions of years. However, before the 1700s, human activities added relatively little excess greenhouse gases. Between the 1700s and the 2020s, modern forces such as industrialization, mechanized transportation, and overpopulation led to a steady growth of greenhouse gas emission. Evidence of climate change has increased correspondingly. Although the world’s climate changes naturally over time, most scientists see a definite correlation between human activities and potentially dangerous shifts in Earth’s balances.

Around 1850, driven by the Industrial Revolution, the United Kingdom (UK) emitted the most carbon dioxide, the most abundant greenhouse gas. Around 1911, the United States and its increasingly industrialized, urbanized society became the top producer, only to be surpassed by China in the 2000s. Although the United States is the second-highest polluter in the 2020s, it is responsible for the great majority of the overall existing human-caused greenhouse gas pollution (Reuters).

In the 1960s, rising awareness of humanity’s impact on nature led to the environmentalist movement. Scientists discovered the nature and effects of greenhouse gases, particularly those emitted through human behaviors, and began speculating on their ultimate effects. In the coming decades, scientists, governments, and organizations worldwide acknowledged that human activity was causing dangerous climatic changes.

In 1992, the United Nations Framework Convention on Climate Change spoke out against the dangers of greenhouse gases and called for serious and prompt reductions in their emission. The Kyoto Protocol was an agreement that sought to put this recommendation into action in the late 1990s. In 2015, the Paris Agreement built upon prior declarations, which set guidelines for countries to reduce greenhouse gas emissions. A large international coalition signed this agreement, though their subsequent adhesion to its standards varies. The United States notably withdrew from the Paris Agreement in 2017, only to re-enter in 2021.

In the 2000s, environmental education and pushes for “green energy” have contributed to some progress in greenhouse gas limitations. Improved technology and widespread awareness caused several forms of emissions to decline by the 2020s. The COVID-19 pandemic that began in the spring of 2020 and caused almost worldwide lockdowns and travel limitations predictably caused a notable drop in greenhouse gas emissions globally. However, by June of 2022, resuming economic and industrial activity brought emission levels back up again. Governments such as those of the United States and Australia responded with legislation to renew their commitment to greenhouse gas reduction through policies such as tax credits for low-carbon energy producers.

Scientists, governments, and organizations have set out many strategies for reducing greenhouse gas emissions. These include new technology with increased efficiency that creates less pollution, as well as “green technology” and renewable, low-emission energy sources such as water, solar, and wind power. Recommendations can guide agriculturalists to more-efficient land management and reduce deforestation to allow trees and other plant life to naturally filter greenhouse gases from the air.

Other recommendations include planting trees, capturing carbon dioxide emissions from factories and power plants before it escapes into the atmosphere, and using vacuum-like machines that can suck in and filter air to remove harmful gases. Although many of these policies target big businesses and entire countries, much of the responsibility for greenhouse gas limitation falls to individuals. All people can play a role in this crucial process simply by conserving the energy they use, such as by reducing the use of oil-powered vehicles, or by shutting off electrical appliances when not in use.

About the Author

Mark Dziak is a Pennsylvania-based writer. He earned his bachelor of arts degree in English from King’s College in Wilkes-Barre, PA, in 2003, and completed a secondary education program there in 2011. He has worked at Northeast Editing, Inc., since 2004. As a content developer, he has researched and written hundreds of educational articles, test items, and other resources on a wide variety of social science topics. In his spare time, Dziak has also published numerous works of nonfiction and fiction.

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