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Concept
Carbon dioxide in Earth's atmosphere
Résumé
In Earth's atmosphere, carbon dioxide is a trace gas that plays an integral part in the greenhouse effect, carbon cycle, photosynthesis and oceanic carbon cycle. It is one of several greenhouse gases in the atmosphere of Earth. The current global average concentration of CO2 in the atmosphere is (0.04%) 421 ppm as of May 2022. This is an increase of 50% since the start of the Industrial Revolution, up from 280 ppm during the 10,000 years prior to the mid-18th century. The increase is due to human activity. Burning fossil fuels is the main cause of these increased CO2 concentrations and also the main cause of climate change. Other large anthropogenic sources include cement production, deforestation, and biomass burning.
While transparent to visible light, carbon dioxide is a greenhouse gas, absorbing and emitting infrared radiation at its two infrared-active vibrational frequencies. absorbs and emits infrared radiation at wavelengths of 4.26 μm (2,347 cm−1) (asymmetric stretching vibrational mode) and 14.99 μm (667 cm−1) (bending vibrational mode). It plays a significant role in influencing Earth's surface temperature through the greenhouse effect. Light emission from the Earth's surface is most intense in the infrared region between 200 and 2500 cm−1, as opposed to light emission from the much hotter Sun which is most intense in the visible region. Absorption of infrared light at the vibrational frequencies of atmospheric traps energy near the surface, warming the surface and the lower atmosphere. Less energy reaches the upper atmosphere, which is therefore cooler because of this absorption.
Increases in atmospheric concentrations of and other long-lived greenhouse gases such as methane, nitrous oxide and ozone increase the absorption and emission of infrared radiation by the atmosphere, causing the observed rise in average global temperature and ocean acidification. Another direct effect is the CO2 fertilization effect. These changes cause a range of indirect effects of climate change on the physical environment, ecosystems and human societies.
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