Carbon dioxide in Earth's atmosphere
Carbon dioxide (CO2) is a significant greenhouse gas in Earth's atmosphere and plays a major role in global warming. It naturally occurs as a by-product of respiration and the combustion of organic materials, but its concentration has increased dramatically due to human activities, particularly the burning of fossil fuels for energy. As of 2023, the global average atmospheric CO2 level reached a record 419.3 parts per million, a significant rise from historical levels. This increase is primarily attributed to industrialization, which has relied heavily on fossil fuels such as coal, oil, and natural gas.
The contributions to CO2 emissions also stem from land use changes, including deforestation and agricultural practices, which release stored carbon into the atmosphere. Notably, industrialized nations have historically been the largest contributors to CO2 emissions, although rapidly developing countries are also significant players. Addressing CO2 emissions poses a complex challenge, as it requires balancing economic development with environmental sustainability. Projections suggest that without intervention, CO2 levels could rise sharply, leading to potentially severe climate consequences by the end of the century.
Carbon dioxide in Earth's atmosphere
Carbon dioxide is the greenhouse gas that contributes the most to global warming. A naturally occurring gas, it is also a by-product of burning fossil fuels, which has become the most important determinant of its rate of increase in Earth’s atmosphere. In 2023, global average atmospheric carbon dioxide reached a record 419.3 parts per million.
Background
Carbon is one of the building blocks of life on Earth; all plants and animals are composed largely of carbon. Carbon dioxide (CO2) emission is a normal part of the respiration cycle. CO2 is also emitted from the burning of plant or animal material. The burning of fossil fuels for energy causes CO2 to be emitted into the atmosphere, and also results in a net increase in atmospheric CO2. Once in the atmosphere, CO2 acts as a greenhouse gas (GHG), trapping heat in the atmosphere and contributing to global warming. Presently, CO2 is the most common GHG in the atmosphere, and its atmospheric concentration is growing rapidly. The proper regulation of human activities that exacerbate this situation is, therefore, the focus of a good deal of attention.
Fossil Fuels
Burning is the major contributor to the contribution of CO2 in the atmosphere. Approximately 65 percent of GHGs are CO2 generated by burning fossil fuels. Another 17 percent comes from the decay of and deforestation. The has indicated with a high degree of confidence that human activities since 1750 have contributed to the addition of these and other GHGs to the atmosphere. When the scientist Charles Keeling began measuring the accumulation of CO2 in the atmosphere from an observatory atop Mauna Loa, Hawaii, in 1958, his measurements indicated that the concentration of CO2 in the atmosphere was 315 parts per million. By 2005, the measured concentration of CO2 was 379 parts per million, which exceeded the natural range of atmospheric CO2 levels over the last 650,000 years. The CO2 content of the atmosphere, derived from ice-core data, has varied over time by 10 parts per million, around a mean value of 280 parts per million.
Industrialization was initially fueled by coal in the eighteenth and nineteenth centuries. Coal continued to be a major source of energy for much of the twentieth century, but oil and natural gas also began to be used for energy in increasing amounts. Gasoline, derived from oil, fueled the growth of automobile culture in many parts of the world in the twentieth century. One thing that all of these energy sources have in common is that they are fossil fuels. Combustion of fossil fuels produces CO2, along with smaller quantities of other GHGs. Much of industrial civilization in the early twenty-first century is powered by fossil fuels.
Some cleaner fuels that do not generate CO2 are available, and more efficient energy sources and automobiles are being built that generate less CO2. However, CO2 will continue to be a by-product of industrial and post-industrial society for years to come. Controlling the impact of CO2 on global climate will require different approaches to energy generation and consumption, as well as new technologies such as that remove carbon from the atmosphere.
Land Use
Human use of the land has led to the accumulation of CO2 (and methane, another GHG) in the atmosphere for a period extending back several thousand years. The growth of the population in the last two hundred years has magnified this impact. Clearing forested land for agriculture has generally led to the burning of much of the cleared vegetation. As noted above, combustion of carbon-based entities produces CO2 as a by-product. The decay of biomass, often generated by agriculture, also produces CO2. As societies have increased their use of metals over time, metal smelting—first using wood for its energy source, then coal—has also contributed CO2 to the atmosphere.
Some of the CO2 that has been anthropogenically generated has been fixed in the oceans and wetlands as peat, rather than in the atmosphere. As wetlands are drained for other uses, however, this carbon sink is diminished, so that more carbon enters the atmosphere. Population pressure and the demands for agricultural products drive land clearing and wetland degradation in many parts of the world. Land clearing continues to increase dramatically in some parts of the world, such as the Amazon basin in Brazil.
Who Produces CO2?
The industrial nations of the world have been the major producers of CO2 over time. As each nation has industrialized, it has begun burning fossil fuels extensively, as well as clearing land for agriculture. Industrial countries continue to generate most of the world’s CO2, either directly through energy generation and automobile use or indirectly by their demand for agricultural products from other areas, which leads to further land clearing in those areas. Nations that rapidly industrialized in the twenty-first century, such as China and India, have done so largely through the use of fossil fuels. In fact, in the first part of the twenty-first century, China surpassed the United States as the largest consumer of fossil fuels as well as the largest producer of GHGs. Even less-industrialized nations make extensive use of fossil fuels.
Dealing with CO2 emissions will require concerted efforts by industrial countries. Less industrialized nations cannot be expected to forgo the economic progress generated by industrialization, but they too will have to manage their carbon footprints over time.
Context
CO2 is the major driver of what is called the greenhouse effect. Some estimates of the amount of CO2 that will be in the atmosphere by 2100 are as high as 1,000 parts per million if emissions grow unchecked. Such a concentration could produce a global temperature increase of 5° Celsius or more, a change not seen for several million years. Even if the growth of CO2 in the atmosphere is brought somewhat under control, its concentration could still reach 440 parts per million, which could produce a temperature increase of as much as 3° Celsius. Controlling the rate of carbon emissions into the atmosphere without harming people’s economic well-being will be a challenge. Failure to control the growth of carbon emissions will lead to what several authorities consider to be a much different and undesirable life for much of the planet. The production of CO2, which has been the hallmark of economic progress, may lead to economic decay if it is not checked.
Key Concepts
- anthropogenic: created by human action
- fossil fuel: fuels formed by pressure on plant or animal material over time, including oil, gas, and coal
- greenhouse gases (GHGs): gases that trap heat within Earth’s atmosphere, increasing global temperatures
Bibliography
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