![]() Almost all other organisms depend on carbohydrate derived from photosynthesis as their primary source of energy and carbon compounds. Plants and other photoautotrophs use solar energy to produce carbohydrate from atmospheric carbon dioxide and water by photosynthesis. The carbon cycle is a biogeochemical cycle in which carbon is exchanged between the Earth's oceans, soil, rocks and the biosphere. This means that some fraction (a projected 20–35%) of the fossil carbon transferred thus far will persist in the atmosphere as elevated CO 2 levels for many thousands of years after these carbon transfer activities begin to subside. It has an atmospheric lifetime that increases with the cumulative amount of fossil carbon extracted and burned, due to the imbalance that this activity has imposed on Earth's fast carbon cycle. ![]() Carbon dioxide exerts a larger overall warming influence than all of the other greenhouse gases combined. These changes cause a range of indirect effects of climate change on the physical environment, ecosystems and human societies. Another direct effect is the CO 2 fertilization effect. Increases in atmospheric concentrations of CO 2 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. Less energy reaches the upper atmosphere, which is therefore cooler because of this absorption. Absorption of infrared light at the vibrational frequencies of atmospheric CO 2 traps energy near the surface, warming the surface and the lower atmosphere. Light emission from the Earth's surface is most intense in the infrared region between 2 cm −1, as opposed to light emission from the much hotter Sun which is most intense in the visible region. It plays a significant role in influencing Earth's surface temperature through the greenhouse effect. CO 2 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). While transparent to visible light, carbon dioxide is a greenhouse gas, absorbing and emitting infrared radiation at its two infrared-active vibrational frequencies. Other large anthropogenic sources include cement production, deforestation, and biomass burning. ![]() Burning fossil fuels is the main cause of these increased CO 2 concentrations and also the main cause of climate change. 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 current global average concentration of CO 2 in the atmosphere is 421 ppm as of May 2022 (0.04%). It is one of several greenhouse gases in the atmosphere of Earth. 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. However, in 2013 the daily mean concentration of CO 2 in the atmosphere surpassed 400 parts per million ( ppmv) - this level has never been reached since the mid-Pliocene, 2 to 4 million years ago. Carbon dioxide concentrations have varied widely over the Earth's 4.54 billion year history. ![]() Atmospheric CO 2 concentrations measured at Mauna Loa Observatory from 1958 to 2022 (also called the Keeling Curve).
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