Carbon dioxide

• CATEGORIES: Pollutants and toxins; atmosphere and air pollution

DEFINITION: Chemical compound in which molecules are composed of one carbon atom and two oxygen atoms

The increase of carbon dioxide in the Earth’s atmosphere that has been occurring since the Industrial Revolution, if not earlier, has been linked to global warming. International efforts undertaken to limit emissions of carbon dioxide have met with varying degrees of success.

Carbon dioxide (CO₂), a gas that is essential to life on Earth, is generated by the burning of fossil fuels such as wood, oil, and coal and by the decomposition of organic matter. Approximately 57 percent of greenhouse gases, of which CO₂ is one, come from the burning of fossil fuels. Land clearing also contributes to CO₂ in the atmosphere. A large amount of CO₂ is found in deposits in the floors of the Earth’s oceans. When this gas is released into the atmosphere, it remains and helps to trap solar radiation in a process that has been shown to contribute to climate change.

The amount of carbon dioxide in the atmosphere has varied over the life of planet Earth. The CO₂ level in the atmosphere was relatively stable, however, from the end of the last ice age until the nineteenth century, averaging 280 parts per million (ppm). From the start of the Industrial Revolution to the middle of the twentieth century, CO₂ levels grew at a steady rate, and the rate of growth increased in the latter half of the twentieth century. When measurements were first undertaken at the Mauna Loa Observatory in Hawaii in the 1950s, the measured concentration of CO₂ was 315 ppm; by 2008, the concentration stood at 385 ppm. Some scientists estimate that the amount of CO₂ in the Earth’s atmosphere could be as high as 1,000 ppm by the year 2100 if emissions continue to increase unchecked. Such a level could produce global temperatures that are 5 degrees Celsius (9 degrees Fahrenheit) warmer than in the early twenty-first century, a level not seen for several million years. Even a moderate increase to 440 ppm is expected to produce a temperature increase of 3 degrees Celsius (5.4 degrees Fahrenheit).

Industrialized countries such as the United States and Germany are major producers of greenhouse gases—especially CO₂—due to high fossil fuel use. Some industrialized nations have turned increasingly to energy sources that produce less CO₂, such as natural gas. However, industrializing nations such as India and China are also major producers of CO₂, largely because they burn a great deal of coal, which produces more CO₂ than other fossil fuels.

Somewhat surprisingly, the industrializing nation of Brazil is a significant producer of CO₂ due to the clearance of massive areas of land in the Amazon basin for agriculture; this process produces CO₂ as the biomass decomposes or is burned. Other, less industrialized nations in Asia, Africa, and South America also produce CO₂ as they harvest large amounts of timber and clear land for agriculture or mining purposes.

The Kyoto Protocol of 1997, an international agreement aimed at limiting and reducing CO₂ emissions, applied only to industrialized countries and countries such as China and India that exhibited the fastest rates of growth in CO₂ emissions. Although some countries have tried to reduce CO₂ emissions, the United States initially refused to ratify the agreement and, during the presidential administration of George W. Bush (2001-09), was slow to try to limit emissions, arguing that industrial production was more important than potential climate change effects. The delegates to the 2009 United Nations Climate Change Conference, held in Copenhagen, Denmark, attempted to address the issue of regulating CO₂ and other greenhouse gas emissions further, but little was accomplished.

In the mid-2020s, international and U.S. efforts to address rising CO₂ emissions intensified. In 2024 and 2025, the US Department of Energy (DOE) significantly expanded programs to support large-scale carbon capture, utilization, and storage (CCUS) initiatives, and directed air capture technologies designed to remove CO₂ directly from the atmosphere. These investments were part of a broader national strategy to meet climate goals outlined in the Paris Agreement and to reduce greenhouse gas emissions across power generation and industrial sectors. Under the Biden administration, several major projects were launched as part of the Investing in America plan to develop regional carbon management hubs and to accelerate research into methods for safely storing captured CO₂ underground or repurposing it for industrial use. These initiatives reflected a growing recognition that aggressive CO₂ reduction strategies are a significant component of slowing climate change and fostering innovation and energy security in the twenty-first century.

Bibliography

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