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Carbon dioxide (CO2) is a colorless, odorless, incombustible gas that is vital to life on Earth. It is a naturally occurring chemical compound that is present in the atmosphere. Carbon dioxide exists in the Earth's atmosphere at a concentration of approximately 0.04 percent (400 parts per million) by volume. It is produced from human and animal respiration, volcanoes, hot springs, and geysers, and the burning of coal, petroleum, and natural gas, which are commonly known as fossil fuels.[1][2] BackgroundThe above diagram shows carbon movements between land, the atmosphere, and oceans (in billions of tons per year). Yellow numbers indicate natural fluctuations, red numbers indicate human contributions, and white numbers represent stored carbon. The diagram does not include the volcanic and tectonic activity that sequesters and releases carbon (image from NASA). Roughly all of the Earth's atmosphere is made up of five gases: nitrogen, oxygen, water vapor, argon, and carbon dioxide. Carbon dioxide is the fourth-most abundant compound in the atmosphere at 0.04 percent. Nitrogen and oxygen are the most abundant compounds at 78 percent and 20.9 percent, respectively. Meanwhile, carbon dioxide is the most abundant gas in the atmospheres of Mars and Venus.[3][4] The global carbon cycle is the exchange of carbon dioxide between the Earth's atmosphere, land, oceans, and fossil fuels, all of which emit and absorb CO2. For example, plants and some microbes use carbon dioxide in photosynthesis, the process by which these organisms create food. These organisms then emit oxygen as a byproduct of photosynthesis. Forests and parts of the ocean, which support photosynthetic organisms, act as carbon sinks that remove carbon dioxide from the atmosphere through photosynthesis. The early atmosphere of Earth had significantly higher carbon dioxide levels compared to now and contained nearly no oxygen. The emergence of photosynthetic organisms like plants led to increased oxygen levels in the atmosphere, allowing the development of oxygen-breathing organisms such as plants, animals, and human beings.[3] Two significant natural sources of carbon dioxide are volcanos and wildfires. Respiration, the process by which organisms convert food into energy, releases carbon dioxide. The combustion of coal, petroleum, and natural gas, including internal combustion engines, also emit carbon dioxide.[3] Common products that use pressurized carbon dioxide include bicycle tires, life jackets, and paintball guns. Carbon dioxide is used to produce soda pop and is created by yeast during fermentation in the production of alcoholic beverages. Because it is inflammable, carbon dioxide is used in some fire extinguishers.[3] Historical concentration of carbon dioxideScientists have attempted to calculate the historical concentration of carbon dioxide in the atmosphere in the distant past as a comparison to recent concentrations. According to the GEOCARB model, which is a well-known geochemical model developed by scientist Robert Berner at Yale University to measure the geologic carbon cycle, carbon dioxide levels in the Ordovician period (420 million to 450 million years ago) were greater than 4,000 parts per million (ppm). Carbon dioxide levels in the Jurassic-Cretaceous periods (132 million to 151 million years ago) were 2,000 ppm. According to Berner, however, there are uncertainties in the model because the periods occurred so long ago, and the model does not take into account short-term carbon dioxide fluctuations during those periods.[5][6][7] Between 1750 and 2015, the atmospheric concentration of carbon dioxide rose from approximately 275-280 parts per million (ppm) to approximately 400 ppm. The historical estimates are based on measurements of air in polar ice sheets. Another estimate of atmospheric carbon dioxide comes from the Mauna Loa Observatory in Hawaii. In 1960, the atmospheric concentration of carbon dioxide was approximately 316 ppm. In 2015, the concentration was approximately 400 ppm. The chart below details the estimated concentration of carbon dioxide each year since 1960.[8][9] Carbon dioxide and greenhouse gasesThe five naturally present greenhouse gases are water vapor, ozone, carbon dioxide, methane, and nitrous oxide. As a greenhouse gas, carbon dioxide captures radiant energy in the atmosphere. This phenomenon, known as the greenhouse effect, occurs when radiation that is attempting to enter into space is trapped in the atmosphere. Without carbon dioxide and other greenhouse gases, Earth would be much colder and inhospitable to life.[3] The most important greenhouse gas is water vapor because it is the largest contributor to the greenhouse effect. According to the American Chemical Society, water vapor accounts for approximately 60 percent of the warming caused by the greenhouse effect. The global average concentration of water vapor, however, is difficult to measure because it varies between seasons and between one place and another, though a warmer atmosphere will likely contain more water vapor.[10][11] The table below shows an estimate of the tropospheric concentration of the four other greenhouse gases in the pre-industrial era (pre-1750) and the estimate of the tropospheric concentration of these gases measured in April 2016. The figures come from the Carbon Dioxide Information Analysis Center at the U.S. Department of Energy and were calculated using data from the United Nations' Intergovernmental Panel on Climate Change (IPCC). The carbon dioxide concentration given is the average for the year 2015 from the U.S. National Oceanic and Atmospheric Administration (NOAA).[10]
Carbon dioxide and global warmingScientists study the relationship between carbon dioxide concentrations in the atmosphere and global temperatures to determine how higher CO2 levels may contribute or have contributed to global warming (defined as a rise in global average temperature). Equilibrium climate sensitivity (ECS) is a metric to calculate global average temperature changes due to higher CO2 concentrations. Specifically, scientists use ECS to determine how the global average temperature (which is calculated from various temperature measurements around the globe) may respond to a doubling of CO2 in the atmosphere, taking into account multiple climatic factors. ECS is calculated using computer-generated simulations known as climate models.[12] The discussion over carbon dioxide and global warming focuses on the precise role of CO2 emissions in global temperatures compared to other climatic factors. Below are summaries of different scientific views on the role of CO2 in global warming:
Recent newsThe link below is to the most recent stories in a Google news search for the terms Carbon dioxide. These results are automatically generated from Google. Ballotpedia does not curate or endorse these articles. See alsoFootnotes
What is the current concentration of CO2 in the atmosphere 2022?[+] Carbon dioxide measured at NOAA's Mauna Loa Atmospheric Baseline Observatory peaked for 2022 at 420.99 parts per million in May, an increase of 1.8 parts per million over 2021, pushing the atmosphere further into territory not seen for millions of years.
What is the current atmospheric CO2 concentration 2020?The global surface average for carbon dioxide (CO2), calculated from measurements collected at NOAA's remote sampling locations, was 412.5 parts per million (ppm) in 2020, rising by 2.6 ppm during the year. The global rate of increase was the fifth-highest in NOAA's 63-year record, following 1987, 1998, 2015 and 2016.
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