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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 carbon dioxide (CO2) in the atmosphere is 421 ppm as of May 2022 (0.04%). 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.
The carbonate–silicate geochemical cycle, also known as the inorganic carbon cycle, describes the long-term transformation of silicate rocks to carbonate rocks by weathering and sedimentation, and the transformation of carbonate rocks back into silicate rocks by metamorphism and volcanism. Carbon dioxide is removed from the atmosphere during burial of weathered minerals and returned to the atmosphere through volcanism. On million-year time scales, the carbonate-silicate cycle is a key factor in controlling Earth's climate because it regulates carbon dioxide levels and therefore global temperature.
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David C. Catling is a Professor in Earth and Space Sciences at the University of Washington. He is a planetary scientist and astrobiologist whose research focuses on understanding the differences between the evolution of planets, their atmospheres, and their potential for life. He has participated in NASA's Mars exploration program and contributed research to help find life elsewhere in the solar system and on planets orbiting other stars. He is also known for his work on the evolution of Earth's atmosphere and biosphere, including how Earth's atmosphere became rich in oxygen, allowing complex life to evolve, and conditions conducive to the origin of life.
Chemical cycling describes systems of repeated circulation of chemicals between other compounds, states and materials, and back to their original state, that occurs in space, and on many objects in space including the Earth. Active chemical cycling is known to occur in stars, many planets and natural satellites.
The prebiotic atmosphere is the second atmosphere present on Earth before today's biotic, oxygen-rich third atmosphere, and after the first atmosphere of Earth's formation. The formation of the Earth, roughly 4.5 billion years ago, involved multiple collisions and coalescence of planetary embryos. This was followed by a <100 million year period on Earth where a magma ocean was present, the atmosphere was mainly steam, and surface temperatures reached up to 8,000 K (14,000 °F). Earth's surface then cooled and the atmosphere stabilized, establishing the prebiotic atmosphere. The environmental conditions during this time period were quite different from today: the Sun was ~30% dimmer overall yet brighter at ultraviolet and x-ray wavelengths, there was a liquid ocean, it is unknown if there were continents but oceanic islands were likely, Earth's interior chemistry was different, and there was a larger flux of impactors hitting Earth's surface.
The Neoproterozoic Oxygenation Event (NOE), also called the Second Great Oxidation Event, was a time interval between around 850 and 540 million years ago which saw a very significant increase in oxygen levels in Earth's atmosphere and oceans. Bringing an end to the Boring Billion, a period of extremely low atmospheric oxygen spanning from the Statherian to the Tonian, the NOE was the second major increase in atmospheric and oceanic oxygen concentration on Earth, though it was not as large as the Great Oxidation Event (GOE) of the Neoarchean-Paleoproterozoic boundary. Unlike the GOE, it is unclear whether the NOE was a synchronous, global event or a series of asynchronous, regional oxygenation intervals with unrelated causes.
References
- ↑ Berner, Robert A. (1998). "The carbon cycle and CO
2 over Phanerozoic time: the role of land plants". Philosophical Transactions of the Royal Society. 353 (1365): 75–82. doi:10.1098/Rstb.1998.0192. PMC 1692179 . - ↑ Berner, Robert A. (1997). "The rise of plants: their effect on weathering and atmospheric CO
2". Science. 276: 544–546. doi:10.1126/Science.276.5312.544. S2CID 128649732. - ↑ Beerling, David J.; Berner, Robert A. (2005). "Feedbacks and the coevolution of plants and atmospheric CO
2". Proceedings of the National Academy of Sciences. 102 (5). USA: 1302–1305. Bibcode:2005PNAS..102.1302B. doi: 10.1073/Pnas.0408724102 . PMC 547859 . PMID 15668402. - ↑ Som, Sanjoy M.; Catling, David C.; Harnmeijer, Jelte P.; Polivka, Peter M.; Buick, Roger (2012). "Air density 2.7 billion years ago limited to less than twice modern levels by fossil raindrop imprints". Nature. 484.7394 (7394): 359–362. Bibcode:2012Natur.484..359S. doi:10.1038/nature10890. PMID 22456703. S2CID 4410348.
- ↑ Som, Sanjoy M.; Buick, Roger; Hagadorn, James W.; Blake, Tim S.; Perreault, John M.; Harnmeijer, Jelte P.; Catling, David C. (2016). "Earth's air pressure 2.7 billion years ago constrained to less than half of modern levels". Nature Geoscience. 9 (6): 448–451. Bibcode:2016NatGe...9..448S. doi:10.1038/ngeo2713.
- ↑ Blamey, Nigel J. F.; Brand, Uwe; Parnell, John; Spear, Natalie; Lécuyer, Christophe; Benison, Kathleen; Meng, Fanwei; Ni, Pei (2016). "Paradigm shift in determining Neoproterozoic atmospheric oxygen". Geology. 44 (8): 651. Bibcode:2016Geo....44..651B. doi: 10.1130/G37937.1 . hdl: 2164/6234 .