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Carbon dioxide Carbon dioxide (chemical formula A chemical formula is a way of presenting information about the chemical proportions of s that constitute a particular or molecule, using symbols, numbers, and sometimes also other symbols, such as pare ...

Carbon dioxide
() is an important
trace gas #REDIRECT Trace gas#REDIRECT Trace gas Trace gases are those gases in the atmosphere other than nitrogen Nitrogen is the chemical element with the Symbol (chemistry), symbol N and atomic number 7. It was first discovered and isolated by Scotti ...
in
Earth's atmosphere The atmosphere of Earth is the layer of gas Gas is one of the four fundamental states of matter (the others being solid Solid is one of the four fundamental states of matter (the others being liquid, gas and plasma). The mo ...
. It is an integral part of the
carbon cycle The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and Earth's atmosphere, atmosphere of the Earth. Carbon is the main component of biological compounds as well as ...

carbon cycle
, a biogeochemical cycle in which
carbon Carbon (from la, carbo "coal") is a with the C and 6. It is lic and —making four s available to form s. It belongs to group 14 of the periodic table. Carbon makes up only about 0.025 percent of Earth's crust. Three occur naturally, ...

carbon
is exchanged between the Earth's
oceans The ocean (also the sea The sea, connected as the world ocean or simply the ocean The ocean (also the sea or the world ocean) is the body of salt water which covers approximately 71% of the surface of the Earth.
, soil, rocks and the
biosphere The biosphere (from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is ap ...
.
Plant Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy that, through cellular respiration, can later be released to fuel ...

Plant
s and other
photoautotrophPhotoautotrophs are organisms that use light energy and inorganic carbon to produce organic materials. Eukaryotic photoautotrophs utilize absorb energy through the chlorophyll molecules in their chloroplasts while prokaryotic photoautotrophs use chlo ...
s use solar energy to produce carbohydrate from atmospheric carbon dioxide and water by
photosynthesis Photosynthesis is a process used by plants and other organisms to convert Conversion or convert may refer to: Arts, entertainment, and media * Conversion (Doctor Who audio), "Conversion" (''Doctor Who'' audio), an episode of the audio drama ' ...

photosynthesis
. Almost all other organisms depend on carbohydrate derived from photosynthesis as their primary source of energy and carbon compounds. absorbs and emits
infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior ...

infrared
radiation at
wavelength In physics Physics is the that studies , its , its and behavior through , and the related entities of and . "Physical science is that department of knowledge which relates to the order of nature, or, in other words, to the regular su ...

wavelength
s of 4.26 μm (2347 cm−1) (asymmetric stretching
vibrational mode A normal mode of an oscillating system is a pattern of motion in which all parts of the system move sinusoidal A sine wave or sinusoid is any of certain mathematical curves that describe a smooth periodic oscillation Oscillation is the repe ...

vibrational mode
) and 14.99 μm (666 cm−1) (bending vibrational mode) and consequently is a
greenhouse gas A greenhouse gas (GHG or GhG) is a gas that Absorption (electromagnetic radiation), absorbs and Emission (electromagnetic radiation), emits radiant energy within the thermal infrared range, causing the greenhouse effect. The primary greenhou ...
that plays a significant role in influencing
Earth Earth is the third planet from the Sun and the only astronomical object known to harbour and support life. 29.2% of Earth's surface is land consisting of continents and islands. The remaining 70.8% is Water distribution on Earth, covered wi ...

Earth
's surface temperature through the
greenhouse effect The greenhouse effect is the process by which radiation from a planet's atmosphere warms the planet's surface to a temperature above what it would be without this atmosphere. Radiatively active gases (i.e., greenhouse gas A greenhou ...

greenhouse effect
. Concentrations of in the atmosphere were as high as 4,000
parts per million In science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific method, builds and Taxonomy (general), organizes knowledge in the form of Testability, testable explanations and predictio ...
(ppm, on a molar basis) during the Cambrian period about 500 million years ago to as low as 180 ppm during the
Quaternary glaciation The Quaternary glaciation, also known as the Pleistocene glaciation, is an alternating series of glacial A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age#REDIRECT Ice age {{ ...
of the last two million years. Reconstructed temperature records for the last 420 million years indicate that atmospheric concentrations peaked at ~2000 ppm during the
Devonian The Devonian ( ) is a geologic period and system of the Paleozoic The Paleozoic (or Palaeozoic) Era ( ; from the Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the H ...
(∼400 Myrs ago) period, and again in the
Triassic The Triassic ( ) is a geologic period The geologic time scale (GTS) is a system of chronological dating that classifies Geology, geological strata (stratigraphy) in time. It is used by geologists, paleontology, paleontologists, and other earth ...

Triassic
(220–200 Myrs ago) period. Global annual mean concentration has increased by more than 45% since the start of the
Industrial Revolution The Industrial Revolution was the transition to new manufacturing processes in Great Britain, continental Europe Continental Europe or mainland Europe is the contiguous continent A continent is any of several large landmasse ...
, from 280 ppm during the 10,000 years up to the mid-18th century to 420 ppm as of April 2021. The present concentration is the highest for 14 million years. The increase has been attributed to
human activity Human behavior is the potential and expressed capacity ( mentally, physically, and socially Social organisms, including humans, live collectively in interacting populations. This interaction is considered social whether they are aware of it ...
, particularly
deforestation deforestation in 1750-2004 (net loss) showing anthropogenic modification of remaining forest. File:MODIS (2020-08-01).jpg, 300px, Dry seasons, exacerbated by climate change, and the use of slash-and-burn methods for clearing tropical forest ...

deforestation
and the burning of
fossil fuels A fossil fuel is a hydrocarbon In organic chemistry Organic chemistry is a branch of chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and ...
. This increase of and other long-lived greenhouse gases in Earth's atmosphere has produced the current episode of
global warming Contemporary climate change includes both the global warming caused by humans, and its impacts on Earth's weather patterns. There have been previous periods of climate change, but the current changes are more rapid than any known even ...

global warming
. Between 30% and 40% of the released by humans into the atmosphere dissolves into the oceans, wherein it forms
carbonic acid In chemistry, carbonic acid is a dibasic acid with the chemical formula A chemical formula is a way of presenting information about the chemical proportions of s that constitute a particular or molecule, using symbols, numbers, and s ...

carbonic acid
and effects changes in the oceanic pH balance.


Current concentration

Carbon dioxide concentrations have shown several cycles of variation from about 180 parts per million during the deep glaciations of the
Holocene The Holocene ( ) is the current geological epoch In geochronology, an epoch is a subdivision of the geologic timescale that is longer than an age (geology), age but shorter than a period (geology), period. The current epoch is the Holocene E ...
and
Pleistocene The Pleistocene ( , often referred to as the ''Ice Age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the earth’s most recent period of repeated glaciations. Before a change finally ...
to 280 parts per million during the interglacial periods. Following the start of the
Industrial Revolution The Industrial Revolution was the transition to new manufacturing processes in Great Britain, continental Europe Continental Europe or mainland Europe is the contiguous continent A continent is any of several large landmasse ...
, atmospheric concentration increased to over 400 parts per million and continues to increase, causing the phenomenon of
global warming Contemporary climate change includes both the global warming caused by humans, and its impacts on Earth's weather patterns. There have been previous periods of climate change, but the current changes are more rapid than any known even ...

global warming
. , the average monthly level of in Earth's atmosphere exceeded 413 parts per million. The daily average concentration of atmospheric at
Mauna Loa Observatory The Mauna Loa Observatory (MLO) is an Earth's atmosphere, atmospheric baseline station on Mauna Loa, on the island of Hawaii (island), Hawaii, located in the U.S. state of Hawaii. The observatory Since 1958, initially under the direction of ...

Mauna Loa Observatory
first exceeded 400 ppm on 10 May 2013 although this concentration had already been reached in the Arctic in June 2012. Each part per million by volume of in the atmosphere represents approximately 2.13
gigatonne The tonne ( or ; symbol: t) is a metric unit of mass equal to 1,000 kilogram The kilogram (also kilogramme) is the base unit of mass Mass is the quantity Quantity is a property that can exist as a multitude or magnitud ...
s of carbon, or 7.82 gigatonnes of . As of 2018, constitutes about 0.041% by volume of the atmosphere, (equal to 410 ppm) which corresponds to approximately 3210 gigatonnes of , containing approximately 875 gigatonnes of carbon. The global mean concentration is currently rising at a rate of approximately 2 ppm/year and accelerating. The current growth rate at Mauna Loa is 2.50 ± 0.26 ppm/year (mean ± 2 std dev). As seen in the graph to the right, there is an annual fluctuation – the level drops by about 6 or 7 ppm (about 50 Gt) from May to September during the
Northern Hemisphere The Northern Hemisphere is the half of Earth Earth is the third planet from the Sun and the only astronomical object known to harbour and support life. 29.2% of Earth's surface is land consisting of continents and islands. The remain ...

Northern Hemisphere
's growing season, and then goes up by about 8 or 9 ppm. The Northern Hemisphere dominates the annual cycle of concentration because it has much greater land area and plant biomass than the
Southern Hemisphere The Southern Hemisphere is the half (hemisphere Hemisphere may refer to: * A half of a sphere As half of the Earth * A hemispheres of Earth, hemisphere of Earth ** Northern Hemisphere ** Southern Hemisphere ** Eastern Hemisphere ** Western He ...

Southern Hemisphere
. Concentrations reach a peak in May as the Northern Hemisphere spring greenup begins, and decline to a minimum in October, near the end of the growing season. Since global warming is attributed to increasing atmospheric concentrations of greenhouse gases such as and methane, scientists closely monitor atmospheric concentrations and their impact on the present-day biosphere. The ''
National Geographic ''National Geographic'' (formerly the ''National Geographic Magazine'', sometimes branded as NAT GEO) is an American monthly magazine published by the National Geographic Society The National Geographic Society (NGS), headquartered in Was ...
'' wrote that the concentration of carbon dioxide in the atmosphere is this high "for the first time in 55 years of measurement—and probably more than 3 million years of Earth history." The current concentration may be the highest in the last 20 million years.


Past concentration

Carbon dioxide concentrations have varied widely over the Earth's 4.54 billion year history. It is believed to have been present in Earth's first atmosphere, shortly after Earth's formation. The second atmosphere, consisting largely of
nitrogen Nitrogen is the chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science ...

nitrogen
and was produced by outgassing from
volcanism Volcanism (or volcanicity) is the phenomenon of eruption of molten rock (magma Magma () is the molten or semi-molten natural material from which all igneous rock Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magma ...
, supplemented by gases produced during the
late heavy bombardment The Late Heavy Bombardment (LHB), or lunar cataclysm, is a hypothesized event thought to have occurred approximately 4.1 to 3.8 billion year A year is the orbital period The orbital period is the time a given astronomical object takes ...
of Earth by huge
asteroids An asteroid is a minor planet A minor planet is an astronomical object in direct orbit around the Sun (or more broadly, any star with a planetary system) that is neither a planet nor exclusively classified as a comet. Before 2006, the Int ...

asteroids
. A major part of carbon dioxide emissions were soon dissolved in water and incorporated in carbonate sediments. The production of free oxygen by
cyanobacteria Cyanobacteria (), also known as Cyanophyta, are a phylum In biology, a phylum (; plural The plural (sometimes list of glossing abbreviations, abbreviated ), in many languages, is one of the values of the grammatical number, grammatical ...

cyanobacteria
l photosynthesis eventually led to the oxygen catastrophe that ended Earth's second atmosphere and brought about the Earth's third atmosphere (the modern atmosphere) 2.4 billion years before the present. Carbon dioxide concentrations dropped from 4,000 parts per million during the
Cambrian period The Cambrian Period ( ; sometimes symbolized Ꞓ) was the first geological period A geological period is one of the several subdivisions of geologic time enabling cross-referencing of rocks and geologic events from place to place. These peri ...
about 500 million years ago to as low as 180 parts per million during the
Quaternary glaciation The Quaternary glaciation, also known as the Pleistocene glaciation, is an alternating series of glacial A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age#REDIRECT Ice age {{ ...
of the last two million years.


Drivers of ancient-Earth carbon dioxide concentration

On long timescales, atmospheric concentration is determined by the balance among
geochemical processes Geochemistry is the science that uses the tools and principles of chemistry to explain the mechanisms behind major geological systems such as the Earth's crust and its oceans. The realm of geochemistry extends beyond the Earth, encompassing the en ...
including organic carbon burial in sediments, silicate rock
weathering Weathering is the deterioration of Rock (geology), rocks, soils and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and biological organisms. Weathering occurs ''in situ'' (on site, with little o ...
, and
volcanic degassing A volcano is a rupture in the Crust (geology), crust of a Planet#Planetary-mass objects, planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and volcanic gas, gases to escape from a magma chamber below the surface. On Ea ...
. The net effect of slight imbalances in the
carbon cycle The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and Earth's atmosphere, atmosphere of the Earth. Carbon is the main component of biological compounds as well as ...

carbon cycle
over tens to hundreds of millions of years has been to reduce atmospheric . On a timescale of billions of years, such downward trend appears bound to continue indefinitely as occasional massive historical releases of buried carbon due to volcanism will become less frequent (as earth mantle cooling and progressive exhaustion of internal radioactive heat proceed further). The rates of these processes are extremely slow; hence they are of no relevance to the atmospheric concentration over the next hundreds or thousands of years. In billion-year timescales, it is predicted that plant, and therefore animal, life on land will die off altogether, since by that time most of the remaining carbon in the atmosphere will be sequestered underground, and natural releases of by radioactivity-driven tectonic activity will have continued to slow down. The loss of plant life would also result in the eventual loss of oxygen. Some microbes are capable of photosynthesis at concentrations of of a few parts per million and so the last life forms would probably disappear finally due to the rising temperatures and loss of the atmosphere when the
sun The Sun is the star A star is an astronomical object consisting of a luminous spheroid of plasma (physics), plasma held together by its own gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many othe ...
becomes a red giant some four billion years from now.


Measuring ancient-Earth carbon dioxide concentration

The most direct method for measuring atmospheric carbon dioxide concentrations for periods before instrumental sampling is to measure bubbles of air ( fluid or gas inclusions) trapped in the
Antarctic The Antarctic (US English or , UK English or and or ) is a around 's , opposite the region around the . The Antarctic comprises the continent of , the and other located on the or south of the . The Antarctic region includes the , wa ...

Antarctic
or
Greenland Greenland ( kl, Kalaallit Nunaat, ; da, Grønland, ) is an autonomous territory An autonomous administrative division (also referred to as an autonomous area, entity, unit, region, subdivision, or territory) is a subnational administra ...

Greenland
ice sheets. The most widely accepted of such studies come from a variety of Antarctic cores and indicate that atmospheric concentrations were about 260–280 ppmv immediately before industrial emissions began and did not vary much from this level during the preceding 10,000
years A year is the orbital period of a planetary body, for example, the Earth, moving in Earth's orbit, its orbit around the Sun. Due to the Earth's axial tilt, the course of a year sees the passing of the seasons, marked by change in weather, the ...
. The longest
ice core An ice core is a core sample . A pied butcherbird The pied butcherbird (''Cracticus nigrogularis'') is a songbird native to Australia. Described by John Gould in 1837, it is a black and white bird long with a long hooked bill. Its head an ...
record comes from East Antarctica, where ice has been sampled to an age of 800,000 years. During this time, the atmospheric carbon dioxide concentration has varied between 180 and 210 ppm during
ice age An ice age is a long period of reduction in the temperature of Earth Earth is the third planet from the Sun and the only astronomical object known to harbour and support life. 29.2% of Earth's surface is land consisting of continents an ...

ice age
s, increasing to 280–300 ppm during warmer
interglacial An interglacial period (or alternatively interglacial, interglaciation) is a geological interval of warmer global average temperature lasting thousands of years that separates consecutive glacial period A glacial period (alternatively glacial or ...
s. The beginning of human agriculture during the current
Holocene The Holocene ( ) is the current geological epoch In geochronology, an epoch is a subdivision of the geologic timescale that is longer than an age (geology), age but shorter than a period (geology), period. The current epoch is the Holocene E ...
epoch may have been strongly connected to the atmospheric increase after the last ice age ended, a fertilization effect raising plant biomass growth and reducing
stoma In botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the ...

stoma
tal conductance requirements for intake, consequently reducing transpiration water losses and increasing water usage efficiency. Various proxy measurements have been used to attempt to determine atmospheric carbon dioxide concentrations millions of years in the past. These include
boron Boron is a chemical element In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behav ...

boron
and
carbon Carbon (from la, carbo "coal") is a with the C and 6. It is lic and —making four s available to form s. It belongs to group 14 of the periodic table. Carbon makes up only about 0.025 percent of Earth's crust. Three occur naturally, ...

carbon
isotope Isotopes are two or more types of atoms that have the same atomic number 300px, The Rutherford–Bohr model of the hydrogen atom () or a hydrogen-like ion (). In this model it is an essential feature that the photon energy (or frequency) of ...
ratios in certain types of marine sediments, and the number of
stomata In botany Botany, also called , plant biology or phytology, is the science of plant life and a branch of biology. A botanist, plant scientist or phytologist is a scientist who specialises in this field. The term "botany" comes from the ...

stomata
observed on fossil plant leaves.
Phytane Phytane is the isoprenoid The terpenoids, also known as isoprenoids, are a large and diverse class of naturally occurring organic chemicals , CH4; is among the simplest organic compounds. In chemistry, organic compounds are generally any chemi ...

Phytane
is a type of
diterpenoid Diterpenes are a class of chemical compounds composed of four isoprene Isoprene, or 2-methyl-1,3-butadiene, is a common organic compound with the formula CH2=C(CH3)−CH=CH2. In its pure form it is a colorless volatile liquid. Isoprene is an un ...
alkane In organic chemistry Organic chemistry is a branch of chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, pr ...
. It is a breakdown product of chlorophyll and is now used to estimate ancient levels. Phytane gives both a continuous record of concentrations but it also can overlap a break in the record of over 500 million years. There is evidence for high concentrations between 200 and 150 million years ago of over 3,000 ppm, and between 600 and 400 million years ago of over 6,000 ppm.IPCC: Climate Change 2001: The Scientific Basis
/ref> In more recent times, atmospheric concentration continued to fall after about 60 million years ago. About 34 million years ago, the time of the
Eocene–Oligocene extinction event The Eocene–Oligocene extinction event, the transition between the end of the Eocene The Eocene ( ) Epoch is a geological epoch In chronology 222px, Joseph Scaliger's ''De emendatione temporum'' (1583) began the modern science of chronol ...
and when the
Antarctic ice sheet The Antarctic ice sheet is one of the two polar ice cap A polar ice cap or polar cap is a high-latitude In geography Geography (from Greek: , ''geographia'', literally "earth description") is a field of science devoted to th ...
started to take its current form, was about 760 ppm, and there is geochemical evidence that concentrations were less than 300 ppm by about 20 million years ago. Decreasing concentration, with a tipping point of 600 ppm, was the primary agent forcing Antarctic glaciation. Low concentrations may have been the stimulus that favored the evolution of C4 plants, which increased greatly in abundance between 7 and 5 million years ago. Based on an analysis of fossil leaves, Wagner et al. argued that atmospheric concentrations during the last 7,000–10,000 year period were significantly higher than 300 ppm and contained substantial variations that may be correlated to climate variations. Others have disputed such claims, suggesting they are more likely to reflect calibration problems than actual changes in . Relevant to this dispute is the observation that Greenland ice cores often report higher and more variable values than similar measurements in Antarctica. However, the groups responsible for such measurements (e.g. H.J. Smith et al.) believe the variations in Greenland cores result from ''in situ'' decomposition of
calcium carbonate Calcium carbonate is a chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one chemical element, element held togethe ...

calcium carbonate
dust found in the ice. When dust concentrations in Greenland cores are low, as they nearly always are in Antarctic cores, the researchers report good agreement between measurements of Antarctic and Greenland concentrations.


Atmospheric carbon dioxide and the greenhouse effect

Earth's natural
greenhouse effect The greenhouse effect is the process by which radiation from a planet's atmosphere warms the planet's surface to a temperature above what it would be without this atmosphere. Radiatively active gases (i.e., greenhouse gas A greenhou ...

greenhouse effect
makes life as we know it possible and carbon dioxide plays a significant role in providing for the relatively high temperature that the planet enjoys. The greenhouse effect is a process by which thermal radiation from a planetary atmosphere warms the planet's surface beyond the temperature it would have in the absence of its atmosphere.A concise description of the greenhouse effect is given in the ''Intergovernmental Panel on Climate Change Fourth Assessment Report,'' "What is the Greenhouse Effect?
FAQ 1.3 – AR4 WGI Chapter 1: Historical Overview of Climate Change Science
IPCC Fourth Assessment Report, Chapter 1, p. 115: "To balance the absorbed incoming olarenergy, the Earth must, on average, radiate the same amount of energy back to space. Because the Earth is much colder than the Sun, it radiates at much longer wavelengths, primarily in the infrared part of the spectrum (see Figure 1). Much of this thermal radiation emitted by the land and ocean is absorbed by the atmosphere, including clouds, and reradiated back to Earth. This is called the greenhouse effect."
Stephen H. Schneider, in ''Geosphere-biosphere Interactions and Climate,'' Lennart O. Bengtsson and Claus U. Hammer, eds., Cambridge University Press, 2001, , pp. 90–91.
E. Claussen, V.A. Cochran, and D.P. Davis, ''Climate Change: Science, Strategies, & Solutions,'' University of Michigan, 2001. p. 373.
A. Allaby and M. Allaby, ''A Dictionary of Earth Sciences,'' Oxford University Press, 1999, , p. 244.
Without the greenhouse effect, the Earth's temperature would be about compared to Earth's actual surface temperature of approximately 14 °C (57.2 °F). Carbon dioxide is believed to have played an important effect in regulating Earth's temperature throughout its 4.7 billion year history. Early in the Earth's life, scientists have found evidence of liquid water indicating a warm world even though the Sun's output is believed to have only been 70% of what it is today. It has been suggested by scientists that higher carbon dioxide concentrations in the early Earth's atmosphere might help explain this
faint young sun paradox The faint young Sun paradox or faint young Sun problem describes the apparent contradiction between observations of liquid water Water is an Inorganic compound, inorganic, Transparency and translucency, transparent, tasteless, odorless, a ...
. When Earth first formed,
Earth's atmosphere The atmosphere of Earth is the layer of gas Gas is one of the four fundamental states of matter (the others being solid Solid is one of the four fundamental states of matter (the others being liquid, gas and plasma). The mo ...

Earth's atmosphere
may have contained more greenhouse gases and concentrations may have been higher, with estimated
partial pressure In a mixture of gases, each constituent gas has a partial pressure which is the notional pressure of that constituent gas if it alone occupied the entire volume of the original mixture at the same temperature. The total pressure of an ideal gas mix ...
as large as , because there was no bacterial
photosynthesis Photosynthesis is a process used by plants and other organisms to convert Conversion or convert may refer to: Arts, entertainment, and media * Conversion (Doctor Who audio), "Conversion" (''Doctor Who'' audio), an episode of the audio drama ' ...

photosynthesis
to
reduce Reduction, reduced, or reduce may refer to: Science and technology Chemistry * Reduction (chemistry), part of a reduction-oxidation (redox) reaction in which atoms have their oxidation state changed. ** Organic redox reaction, a redox reacti ...

reduce
the gas to carbon compounds and oxygen.
Methane Methane (, ) is a chemical compound with the chemical formula A chemical formula is a way of presenting information about the chemical proportions of s that constitute a particular or molecule, using symbols, numbers, and sometimes a ...
, a very active greenhouse gas which reacts with oxygen to produce and water vapor, may have been more prevalent as well, with a mixing ratio of 10−4 (100
parts per million In science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific method, builds and Taxonomy (general), organizes knowledge in the form of Testability, testable explanations and predictio ...
by volume). Though water is responsible for most (about 36-70%) of the total greenhouse effect, the role of water vapor as a greenhouse gas depends on temperature. On Earth, carbon dioxide is the most relevant, direct anthropologically influenced greenhouse gas. Carbon dioxide is often mentioned in the context of its increased influence as a greenhouse gas since the pre-industrial (1750) era. In the
IPCC Fifth Assessment Report The Intergovernmental Panel on Climate Change (IPCC) is an intergovernmental body of the United Nations The United Nations (UN) is an intergovernmental organization aiming to maintain international peace and international security, s ...
the increase in CO2 was estimated to be responsible for 1.82 W m−2 of the 2.63 W m−2 change in radiative forcing on Earth (about 70%).IPCC Fifth Assessment Report – Chapter 8: Anthropogenic and Natural Radiative Forcing. https://www.ipcc.ch/pdf/assessment-report/ar5/wg1/WG1AR5_Chapter08_FINAL.pdf The concept of atmospheric CO2 increasing ground temperature was first published by
Svante Arrhenius Svante August Arrhenius ( , ; 19 February 1859 – 2 October 1927) was a Swedish Swedish or ' may refer to: * Anything from or related to Sweden, a country in Northern Europe * Swedish language, a North Germanic language spoken primarily in S ...

Svante Arrhenius
in 1896. The increased radiative forcing due to increased CO2 in the Earth's atmosphere is based on the physical properties of CO2 and the non-saturated absorption windows where CO2 absorbs outgoing long-wave energy. The increased forcing drives further changes in Earth's energy balance and, over the longer term, in Earth's climate.


Atmospheric carbon dioxide and the carbon cycle

Atmospheric carbon dioxide plays an integral role in the Earth's carbon cycle whereby is removed from the atmosphere by some natural processes such as
photosynthesis Photosynthesis is a process used by plants and other organisms to convert Conversion or convert may refer to: Arts, entertainment, and media * Conversion (Doctor Who audio), "Conversion" (''Doctor Who'' audio), an episode of the audio drama ' ...

photosynthesis
and deposition of carbonates, to form limestones for example, and added back to the atmosphere by other natural processes such as
respiration Respiration may refer to: Biology * Cellular respiration Cellular respiration is a set of metabolic Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life Life is a characteristic that distingui ...

respiration
and the acid dissolution of carbonate deposits. There are two broad carbon cycles on Earth: the fast carbon cycle and the slow carbon cycle. The fast carbon cycle refers to movements of carbon between the environment and living things in the biosphere whereas the slow carbon cycle involves the movement of carbon between the atmosphere, oceans, soil, rocks, and volcanism. Both cycles are intrinsically interconnected and atmospheric facilitates the linkage. Natural sources of atmospheric include
volcanic A volcano is a rupture in the crust of a planetary-mass object A planet is an astronomical body orbit In physics, an orbit is the gravitationally curved trajectory of an physical body, object, such as the trajectory of a planet a ...

volcanic
outgassing Outgassing (sometimes called offgassing, particularly when in reference to indoor air quality Indoor air quality (IAQ) is the air quality within and around buildings and structures. IAQ is known to affect the health, comfort, and well-being of ...

outgassing
, the
combustion Combustion, or burning, is a high-temperature exothermic redox chemical reaction between a fuel (the reductant) and an oxidant, usually atmospheric oxygen, that produces oxidized, often gaseous products, in a mixture termed as smoke. Combustion ...
of
organic matter Organic matter, organic material, or natural organic matter refers to the large source of carbon-based compounds found within natural and engineered, terrestrial, and aquatic environments. It is matter In classical physics and general che ...
,
wildfires A wildfire, bushfire, wildland fire or rural fire is an unplanned, unwanted, uncontrolled fire BBQ. Fire is the rapid oxidation of a material in the exothermic chemical process of combustion, releasing heat, light, and various reaction ...
and the
respiration Respiration may refer to: Biology * Cellular respiration Cellular respiration is a set of metabolic Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life Life is a characteristic that distingui ...
processes of living
aerobic organism An aerobic organism or aerobe is an organism In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, mol ...
s. Man-made sources of include the burning of
fossil fuels A fossil fuel is a hydrocarbon In organic chemistry Organic chemistry is a branch of chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and ...
for heating,
power generation Electricity generation is the process of generating electric power Electric power is the rate, per unit time, at which electrical energy Electrical energy is energy derived as a result of movement of electrically charged particles. When use ...
and
transport Transport (in British English British English (BrE) is the standard dialect A standard language (also standard variety, standard dialect, and standard) is a language variety that has undergone substantial codification of grammar and ...

transport
, as well as some industrial processes such as cement making. It is also produced by various
microorganism A microorganism, or microbe,, ''mikros'', "small") and ''organism In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes ...
s from
fermentation Fermentation is a metabolic Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life Life is a characteristic that distinguishes physical entities that have biological processes, such as Cell signalin ...
and
cellular respiration Cellular respiration is a set of metabolic Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life Life is a characteristic that distinguishes physical entities that have biological processes, such a ...

cellular respiration
.
Plant Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy that, through cellular respiration, can later be released to fuel ...

Plant
s,
algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic Photosynthesis is a process used by plants and other organisms to convert Conversion or convert may refer to: Arts, entertainment, and media * Co ...

algae
and
cyanobacteria Cyanobacteria (), also known as Cyanophyta, are a phylum In biology, a phylum (; plural The plural (sometimes list of glossing abbreviations, abbreviated ), in many languages, is one of the values of the grammatical number, grammatical ...

cyanobacteria
convert carbon dioxide to
carbohydrate A carbohydrate () is a biomolecule , showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallography by Max Perutz and Sir John Cowdery Kendrew in 1958, for which they received a ...
s by a process called photosynthesis. They gain the energy needed for this reaction from absorption of sunlight by
chlorophyll Chlorophyll (also chlorophyl) is any of several related green pigment A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally ...

chlorophyll
and other pigments. Oxygen, produced as a by-product of photosynthesis, is released into the atmosphere and subsequently used for respiration by
heterotrophic A heterotroph (; from Ancient Greek "other" and "nutrition") is an organism that cannot produce its own food, instead taking nutrition from other sources of organic carbon, mainly plant or animal matter. In the food chain, heterotrophs are prim ...
organisms and other plants, forming a cycle with carbon. Most sources of emissions are natural, and are balanced to various degrees by similar sinks. For example, the decay of organic material in forests, grasslands, and other land vegetation - including the infrequent activity of forest fires - results in the release of about 400 
gigatonnes The tonne ( or ; symbol: t) is a metric unit of mass equal to 1,000 kilogram The kilogram (also kilogramme) is the base unit of mass Mass is the physical quantity, quantity of ''matter'' in a physical body. It is also a meas ...
of (containing 120 billion tonnes carbon) every year, while uptake by new growth on land nearly counteracts these releases. Although much in the early atmosphere of the young Earth was produced by
volcanic activity Volcanism (or volcanicity) is the phenomenon of eruption of molten rock (magma Magma () is the molten or semi-molten natural material from which all igneous rock Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magma ...

volcanic activity
, modern volcanic activity releases only 130 to 230 
megatonnes The tonne ( or ; symbol: t) is a Metric_units#Mass, metric unit of mass equal to 1,000 kilograms. It is also referred to as a metric ton. It is equivalent to approximately international avoirdupois pound, pounds; , and 0.984 long tons ...
of each year. This small natural geologic source is also balanced by natural sinks, in the form of chemical and biological processes which remove from the atmosphere. By contrast, as of year 2019 the extraction and burning of geologic fossil carbon by humans releases over 30 gigatonnes of (9 billion tonnes carbon) each year.Friedlingstein, P., Jones, M., O'Sullivan, M., Andrew, R., Hauck, J., Peters, G., Peters, W., Pongratz, J., Sitch, S., Le Quéré, C. and 66 others (2019) "Global carbon budget 2019". ''Earth System Science Data'', 11(4): 1783–1838. . Material was copied from this source, which is available under
Creative Commons Attribution 4.0 International License
This larger disruption to the natural balance is responsible for recent growth in the atmospheric concentration. Overall, there is a large natural flux of atmospheric into and out of the
biosphere The biosphere (from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is ap ...
, both on land and in the oceans. In the pre-industrial era, each of these fluxes were in balance to such a degree that little net flowed between the land and ocean reservoirs of carbon, and little change resulted in the atmospheric concentration. From the human pre-industrial era to 1940, the terrestrial biosphere represented a net source of atmospheric (driven largely by land-use changes), but subsequently switched to a net sink with growing fossil carbon emissions. In 2012, about 57% of human-emitted , mostly from the burning of fossil carbon, was taken up by land and ocean sinks. The ratio of the increase in atmospheric to emitted is known as the ''airborne fraction'' (Keeling et al., 1995). This ratio varies in the short-term and is typically about 45% over longer (5-year) periods. Estimated carbon in global terrestrial vegetation increased from approximately 740 billion tons in 1910 to 780 billion tons in 1990. By 2009, acidity of the ocean surface increased about 30% due to uptake of emitted fossil .


Atmospheric carbon dioxide and photosynthesis

Carbon dioxide in the Earth's atmosphere is essential to life and to most of the planetary biosphere. Over the course of Earth's geologic history concentrations have played a role in biological evolution. The first photosynthetic organisms probably
evolved Evolution is change in the Heredity, heritable Phenotypic trait, characteristics of biological populations over successive generations. These characteristics are the Gene expression, expressions of genes that are passed on from parent to offs ...

evolved
early in the
evolutionary history of life The history of life on Earth Earth is the third planet from the Sun and the only astronomical object known to harbour and support life. 29.2% of Earth's surface is land consisting of continents and islands. The remaining 70.8% is Water ...
and most likely used
reducing agent A reducing agent (also called a reductant, reducer, or electron donor) is an element or compound that loses or "donates" an electron The electron is a subatomic particle (denoted by the symbol or ) whose electric charge is negative one ele ...
s such as
hydrogen Hydrogen is the chemical element with the Symbol (chemistry), symbol H and atomic number 1. Hydrogen is the lightest element. At standard temperature and pressure, standard conditions hydrogen is a gas of diatomic molecules having the che ...

hydrogen
or
hydrogen sulfide Hydrogen sulfide is a chemical compound A chemical compound is a chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by havi ...

hydrogen sulfide
as sources of electrons, rather than water. Cyanobacteria appeared later, and the excess oxygen they produced contributed to the oxygen catastrophe, which rendered the evolution of complex life possible. In recent geologic times, low concentrations below 600 parts per million might have been the stimulus that favored the evolution of C4 plants which increased greatly in abundance between 7 and 5 million years ago over plants that use the less efficient C3 metabolic pathway. At current atmospheric pressures photosynthesis shuts down when atmospheric concentrations fall below 150 ppm and 200 ppm although some microbes can extract carbon from the air at much lower concentrations. Today, the average rate of energy capture by photosynthesis globally is approximately 130 
terawatts The watt (symbol: W) is a unit of Power (physics), power or radiant flux. In the International System of Units (SI), it is defined as a SI derived unit, derived unit of (in SI base units) 1 kg⋅m2⋅s−3 or, equivalently, 1 joule per second. I ...
, which is about six times larger than the current power consumption of human civilization. Photosynthetic organisms also convert around 100–115 billion metric tonnes of carbon into biomass per year. Photosynthetic organisms are
photoautotrophPhotoautotrophs are organisms that use light energy and inorganic carbon to produce organic materials. Eukaryotic photoautotrophs utilize absorb energy through the chlorophyll molecules in their chloroplasts while prokaryotic photoautotrophs use chlo ...
s, which means that they are able to synthesize food directly from and water using energy from light. However, not all organisms that use light as a source of energy carry out photosynthesis, since ''
photoheterotrophPhotoheterotrophs ('' Gk'': ''photo'' = light, ''hetero'' = (an)other, ''troph'' = nourishment) are heterotrophic phototrophs – that is, they are organisms that use light for energy, but cannot use carbon dioxide Carbon dioxide (chemical form ...
s'' use organic compounds, rather than , as a source of carbon. In plants, algae and cyanobacteria, photosynthesis releases oxygen. This is called ''oxygenic photosynthesis''. Although there are some differences between oxygenic photosynthesis in
plants Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to convert Conversion or convert may refer to: Arts, entertainment, and media * Conversion (Doctor Who audio), "Conversion" (''Docto ...

plants
,
algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic Photosynthesis is a process used by plants and other organisms to convert Conversion or convert may refer to: Arts, entertainment, and media * Co ...

algae
, and
cyanobacteria Cyanobacteria (), also known as Cyanophyta, are a phylum In biology, a phylum (; plural The plural (sometimes list of glossing abbreviations, abbreviated ), in many languages, is one of the values of the grammatical number, grammatical ...

cyanobacteria
, the overall process is quite similar in these organisms. However, there are some types of bacteria that carry out
anoxygenic photosynthesis Bacterial anoxygenic photosynthesis is differentiated from the more renowned terrestrial plant oxygenic photosynthesis by method of a terminal reductant that is (e.g. hydrogen sulfide Hydrogen sulfide is the chemical compound with the chemical f ...
, which consumes but does not release oxygen. Carbon dioxide is converted into sugars in a process called
carbon fixation Carbon fixation or сarbon assimilation is the process by which inorganic carbon (particularly in the form of carbon dioxide Carbon dioxide (chemical formula ) is a colorless gas with a density about 53% higher than that of dry air. Carbon ...
. Carbon fixation is an
endothermic In thermochemistry Thermochemistry is the study of the heat energy which is associated with chemical reaction A chemical reaction is a process that leads to the chemical transformation of one set of chemical substance A chemical substanc ...
redox Redox (reduction–oxidation, pronunciation: or ) is a type of chemical reaction A chemical reaction is a process that leads to the chemical transformation of one set of chemical substance A chemical substance is a form of matter ...

redox
reaction, so photosynthesis needs to supply both the source of energy to drive this process and the electrons needed to convert into a
carbohydrate A carbohydrate () is a biomolecule , showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallography by Max Perutz and Sir John Cowdery Kendrew in 1958, for which they received a ...
. This addition of the electrons is a
reduction reaction Redox (reduction–oxidation, pronunciation: or ) is a type of chemical reaction A chemical reaction is a process that leads to the chemical transformation of one set of chemical substance A chemical substance is a form of matter ...
. In general outline and in effect, photosynthesis is the opposite of
cellular respiration Cellular respiration is a set of metabolic Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life Life is a characteristic that distinguishes physical entities that have biological processes, such a ...

cellular respiration
, in which glucose and other compounds are oxidized to produce and water, and to release
exothermic In thermodynamics Thermodynamics is a branch of physics that deals with heat, Work (thermodynamics), work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation. The behavior of these qu ...

exothermic
chemical energy to drive the organism's
metabolism Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life Life is a characteristic that distinguishes physical entities A bubble of exhaled gas in water In common usage and classical mechanics, a phys ...

metabolism
. However, the two processes take place through a different sequence of chemical reactions and in different cellular compartments. Most organisms that utilize photosynthesis to produce oxygen use
visible light Light or visible light is electromagnetic radiation within the portion of the electromagnetic spectrum that is visual perception, perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nano ...
to do so, although at least three use shortwave
infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior ...

infrared
or, more specifically, far-red radiation.


Effects of increased CO2 on plants and crops

A 1993 review of scientific greenhouse studies found that a doubling of concentration would stimulate the growth of 156 different plant species by an average of 37%. Response varied significantly by species, with some showing much greater gains and a few showing a loss. For example, a 1979 greenhouse study found that with doubled concentration the dry weight of 40-day-old cotton plants doubled, but the dry weight of 30-day-old maize plants increased by only 20%. In addition to greenhouse studies, field and satellite measurements attempt to understand the effect of increased in more natural environments. In free-air carbon dioxide enrichment (FACE) experiments plants are grown in field plots and the concentration of the surrounding air is artificially elevated. These experiments generally use lower levels than the greenhouse studies. They show lower gains in growth than greenhouse studies, with the gains depending heavily on the species under study. A 2005 review of 12 experiments at 475–600 ppm showed an average gain of 17% in crop yield, with
legumes A legume () is a plant Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy that, through cellular respiration, can ...
typically showing a greater response than other species and
C4 plants carbon fixation or the Hatch–Slack pathway is one of three known photosynthetic Photosynthesis is a process used by plants and other organisms to convert Conversion or convert may refer to: Arts, entertainment, and media * Conversion ( ...
generally showing less. The review also stated that the experiments have their own limitations. The studied levels were lower, and most of the experiments were carried out in temperate regions. Satellite measurements found increasing
leaf area index Leaf area index (LAI) is a dimensionless quantity In dimensional analysis In engineering and science, dimensional analysis is the analysis of the relationships between different physical quantities by identifying their base quantity, base quant ...
for 25% to 50% of Earth's vegetated area over the past 35 years (i.e., a greening of the planet), providing evidence for a positive CO2 fertilization effect. A 2017 ''
Politico ''Politico'' (stylized ''POLITICO''), known originally as ''The Politico'', is a political journalism Political journalism is a broad branch of journalism that includes coverage of all aspects of politics and political science, although th ...

Politico
'' article states that increased levels may have a negative impact on the nutritional quality of various human
food crops A crop is a plant that can be grown and harvested extensively for profit or subsistence. Crops may refer either to the harvested parts or to the harvest in a more refined state. Most crops are cultivated in agriculture or aquaculture. A crop ma ...

food crops
, by increasing the levels of
carbohydrate A carbohydrate () is a biomolecule , showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallography by Max Perutz and Sir John Cowdery Kendrew in 1958, for which they received a ...
s, such as
glucose Glucose is a simple with the . Glucose is the most abundant , a subcategory of s. Glucose is mainly made by and most during from water and carbon dioxide, using energy from sunlight, where it is used to make in s, the most abundant carbohydr ...

glucose
, while decreasing the levels of important nutrients such as
protein Proteins are large biomolecule , showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallography by Max Perutz and Sir John Cowdery Kendrew in 1958, for which they received a No ...
,
iron Iron () is a chemical element In chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and s: their composition, structure, properties, behav ...

iron
, and
zinc Zinc is a chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical element ...
. Crops experiencing a decrease in
protein Proteins are large biomolecule , showing alpha helices, represented by ribbons. This poten was the first to have its suckture solved by X-ray crystallography by Max Perutz and Sir John Cowdery Kendrew in 1958, for which they received a No ...
include
rice Rice is the seed A seed is an embryonic ''Embryonic'' is the twelfth studio album by experimental rock band the Flaming Lips released on October 13, 2009, on Warner Bros. Records, Warner Bros. The band's first double album, it was relea ...

rice
,
wheat Wheat is a grass widely cultivated for its seed, a cereal grain which is a worldwide staple food. The many species of wheat together make up the genus ''Triticum''; the most widely grown is common wheat Common wheat (''Triticum aestivum'' ...

wheat
,
barley Barley (''Hordeum vulgare''), a member of the grass family Poaceae () or Gramineae () is a large and nearly ubiquitous family In human society, family (from la, familia) is a group of people related either by consanguinity (by recogn ...

barley
and
potato The potato is a starch#Food, starchy tuber of the plant ''Solanum tuberosum'' and is a root vegetable native to the Americas. The plant is a perennial plant, perennial in the nightshade family Solanaceae. Wild potato species can be found thro ...

potato
es.


Atmospheric carbon dioxide and the oceanic carbon cycle

The Earth's oceans contain a large amount of in the form of bicarbonate and carbonate ions—much more than the amount in the atmosphere. The bicarbonate is produced in reactions between rock, water, and carbon dioxide. One example is the dissolution of calcium carbonate: : + + ⇌ + 2 Reactions like this tend to buffer changes in atmospheric . Since the right side of the reaction produces an acidic compound, adding on the left side decreases the of seawater, a process which has been termed
ocean acidification Ocean acidification is the ongoing decrease in the pH value of the Earth Earth is the third planet from the Sun and the only astronomical object known to harbour and support life. 29.2% of Earth's surface is land consisting of con ...
(pH of the ocean becomes more acidic although the pH value remains in the alkaline range). Reactions between and non-carbonate rocks also add bicarbonate to the seas. This can later undergo the reverse of the above reaction to form carbonate rocks, releasing half of the bicarbonate as . Over hundreds of millions of years, this has produced huge quantities of carbonate rocks. Ultimately, most of the emitted by human activities will dissolve in the ocean; however, the rate at which the ocean will take it up in the future is less certain. Even if equilibrium is reached, including dissolution of carbonate minerals, the increased concentration of bicarbonate and decreased or unchanged concentration of carbonate ion will give rise to a higher concentration of un-ionized carbonic acid and dissolved . This, along with higher temperatures, would mean a higher equilibrium concentration of in the air.


Anthropogenic CO2 emissions

While absorption and release is always happening as a result of natural processes, the recent rise in levels in the atmosphere is known to be mainly due to human (anthropogenic) activity.e.g. There are four ways human activity, especially fossil fuel burning, is known to have caused the rapid increase in atmospheric over the last few centuries: * Various national statistics accounting for fossil fuel consumption, combined with knowledge of how much atmospheric is produced per unit of fossil fuel (e.g. liter of
gasoline Gasoline () or petrol () (see the etymology Etymology ()The New Oxford Dictionary of English ''The'' () is a grammatical article Article often refers to: * Article (grammar) An article is any member of a class of dedicated word ...
). * By examining the ratio of various carbon isotopes in the atmosphere. The burning of long-buried fossil fuels releases containing carbon of different isotopic ratios to those of living plants, enabling distinction between natural and human-caused contributions to concentration. * Higher atmospheric concentrations in the Northern Hemisphere, where most of the world's population lives (and emissions originate from), compared to the southern hemisphere. This difference has increased as anthropogenic emissions have increased. * Atmospheric O levels are decreasing in Earth's atmosphere as it reacts with the carbon in fossil fuels to form . Burning fossil fuels such as
coal Coal is a combustible , Germany ) , image_map = , map_caption = , map_width = 250px , capital = Berlin , coordinates = , largest_city = capital , languages_type = Official language , languages = German language, German , ...

coal
,
petroleum Petroleum, also known as crude oil and oil, is a naturally occurring, yellowish-black liquid A liquid is a nearly incompressible In fluid mechanics or more generally continuum mechanics, incompressible flow (isochoric process, isoc ...

petroleum
, and
natural gas Natural gas (also called fossil gas; sometimes just gas) is a naturally occurring hydrocarbon gas mixture consisting of methane and commonly including varying amounts of other higher alkanes, and sometimes a small percentage of carbon dioxid ...

natural gas
is the leading cause of increased
anthropogenic Anthropogenic ("human" + "generating") is an adjective that may refer to: * Anthropogeny, the study of the origins of humanity Counterintuitively, anthropogenic may also refer to things that have been generated by humans, as follows: * Human im ...
;
deforestation deforestation in 1750-2004 (net loss) showing anthropogenic modification of remaining forest. File:MODIS (2020-08-01).jpg, 300px, Dry seasons, exacerbated by climate change, and the use of slash-and-burn methods for clearing tropical forest ...

deforestation
is the second major cause. In 2010, 9.14 gigatonnes of carbon (GtC, equivalent to 33.5
gigatonne The tonne ( or ; symbol: t) is a metric unit of mass equal to 1,000 kilogram The kilogram (also kilogramme) is the base unit of mass Mass is the quantity Quantity is a property that can exist as a multitude or magnitud ...
s of or about 4.3 ppm in Earth's atmosphere) were released from fossil fuels and cement production worldwide, compared to 6.15 GtC in 1990. In addition, land use change contributed 0.87 GtC in 2010, compared to 1.45 GtC in 1990. In 1997, human-caused Indonesian peat fires were estimated to have released between 13% and 40% of the average annual global carbon emissions caused by the burning of
fossil fuels A fossil fuel is a hydrocarbon In organic chemistry Organic chemistry is a branch of chemistry Chemistry is the study of the properties and behavior of . It is a that covers the that make up matter to the composed of s, s and ...
. In the period 1751 to 1900, about 12 GtC were released as to the atmosphere from burning of fossil fuels, whereas from 1901 to 2013 the figure was about 380 GtC. The Integrated Carbon Observation System (ICOS) continuously releases data about emissions, budget and concentration at individual observation stations. Anthropogenic carbon emissions exceed the amount that can be taken up or balanced out by natural sinks. As a result, carbon dioxide has gradually accumulated in the atmosphere, and , its concentration is almost 48% above pre-industrial levels. Various techniques have been proposed for removing excess carbon dioxide from the atmosphere in
carbon dioxide sink A carbon sink is any reservoir, natural or otherwise, that accumulates and stores some carbon Carbon (from la, carbo "coal") is a with the C and 6. It is lic and —making four s available to form s. It belongs to group 14 of the p ...
s. Currently about half of the carbon dioxide released from the is not absorbed by vegetation and the oceans and remains in the
atmosphere An atmosphere (from the greek words ἀτμός ''(atmos)'', meaning 'vapour', and σφαῖρα ''(sphaira)'', meaning 'ball' or 'sphere') is a layer or a set of layers of gases surrounding a planet or other material body, that is held in ...

atmosphere
. Excess emitted since the pre-industrial era is projected to remain in the atmosphere for centuries to millennia, even after emissions stop. Even if human carbon dioxide emissions were to completely cease, atmospheric temperatures are not expected to decrease significantly for thousands of years. File:Global Carbon Emissions.svg, Global fossil carbon emissions 1800–2014 File:TOMS indonesia smog lrg.jpg,
False-color False color (or pseudo color) refers to a group of color Color (American English American English (AmE, AE, AmEng, USEng, en-US), sometimes called United States English or U.S. English, is the set of varieties of the English ...
image of smoke and ozone pollution from Indonesian fires, 1997 File:Biosphere CO2 Flux 08072006.gif, Biosphere flux in the northern hemisphere winter (NOAA Carbon Tracker) File:Biosphere CO2 Flux 23122006.gif, Biosphere flux in the northern hemisphere summer (NOAA Carbon Tracker)


Ongoing measurements of atmospheric CO2

The first reproducibly accurate measurements of atmospheric CO2 were from flask sample measurements made by Dave Keeling at
Caltech The California Institute of Technology (Caltech)The university itself only spells its short form as "Caltech"; other spellings such a"Cal Tech" and "CalTech" are incorrect. The Institute is also occasionally referred to as "CIT", most notably ...
in the 1950s. A few years later in March 1958 the first ongoing measurements were started by Keeling at
Mauna Loa Mauna Loa ( or ; Hawaiian Hawaiian may refer to: * Hawaii state residents, regardless of ancestry * Native Hawaiians, the current term for the indigenous people of the Hawaiian Islands or their descendants * Hawaiian language Historic uses * ...

Mauna Loa
. Measurements at Mauna Loa have been ongoing since then. Now measurements are made at many sites globally. Additional measurement techniques are also used as well. Many measurement sites are part of larger global networks. Global network data are often made publicly available on the conditions of proper acknowledgment according to the respective data user policies. There are several surface measurement (including flasks and continuous in situ) networks including
NOAA The National Oceanic and Atmospheric Administration (NOAA ) is an American scientific and regulatory agency within the United States Department of Commerce The United States Department of Commerce is an executive department The Unite ...
/ ERSL, WDCGG, and RAMCES. The NOAA/ESRL Baseline Observatory Network, and the
Scripps Institution of Oceanography The Scripps Institution of Oceanography (sometimes referred to as SIO, Scripps Oceanography, or Scripps) in San Diego, California San Diego ( , ; ) is a city in the U.S. state of California on the coast of the Pacific Ocean and immedi ...

Scripps Institution of Oceanography
Network data are hosted at the CDIAC at
ORNL Oak Ridge National Laboratory (ORNL) is a U.S. multiprogram science and technology national laboratory sponsored by the U.S. Department of Energy (DOE) and administered, managed, and operated by UT–Battelle as a federally funded research an ...
. The World Data Centre for Greenhouse Gases (WDCGG), part of GAW, data are hosted by the . The Reseau Atmospherique de Mesure des Composes an Effet de Serre database (RAMCES) is part of IPSL. From these measurements, further products are made which integrate data from the various sources. These products also address issues such as data discontinuity and sparseness. GLOBALVIEW-CO2 is one of these products. Ongoing ground-based total column measurements began more recently. Column measurements typically refer to an averaged column amount denoted XCO2, rather than a surface only measurement. These measurements are made by the TCCON. These data are also hosted on the CDIAC, and made publicly available according to the data use policy.TCCON data use policy webpage https://tccon-wiki.caltech.edu/Network_Policy/Data_Use_Policy. Retrieved 9 February 2016 Satellite measurements are also a recent addition to atmospheric XCO2 measurements.
SCIAMACHY SCIAMACHY (SCanning Imaging Absorption SpectroMeter for Atmospheric CHartographY; Greek: σκιάμάχη: analogously: "Fighting shadows") was one of ten instruments aboard of ESA's ENVIronmental SATellite, ENVISAT. It was a satellite spectromet ...
aboard
ENVISAT Envisat ("Environmental Satellite") is a large inactive Earth-observing satellite which is still in orbit and now considered a space debris. Operated by the European Space Agency , owner = , headquarters = Paris Paris () ...
made global column XCO2 measurements from 2002 to 2012. AIRS aboard NASA's Aqua satellite makes global XCO2 measurements and was launched shortly after ENVISAT in 2012. More recent satellites have significantly improved the data density and precision of global measurements. Newer missions have higher spectral and spatial resolutions. JAXA's
GOSAT The Greenhouse Gases Observing Satellite (GOSAT''), also known as , is an Earth observation satellite An Earth observation satellite or Earth remote sensing satellite is a satellite used or designed for Earth observation (EO) from orbit, inclu ...
was the first dedicated GHG monitoring satellite to successfully achieve orbit in 2009. NASA's
OCO-2 Orbiting Carbon Observatory-2 (OCO-2) is an American environmental science satellite which launched on 2 July 2014. A NASA mission, it is a replacement for the Orbiting Carbon Observatory which was lost in a launch failure in 2009. It is the secon ...

OCO-2
launched in 2014 was the second. Various other satellites missions to measure atmospheric XCO2 are planned.


See also

* Atmospheric carbon cycle *
Carbon cycle The carbon cycle is the biogeochemical cycle by which carbon is exchanged among the biosphere, pedosphere, geosphere, hydrosphere, and Earth's atmosphere, atmosphere of the Earth. Carbon is the main component of biological compounds as well as ...

Carbon cycle
*
Global temperature record The global temperature record shows the fluctuations of the temperature Temperature is a physical quantity that expresses hot and cold. It is the manifestation of thermal energy, present in all matter, which is the source of the occurren ...
*
Keeling Curve #REDIRECT Keeling Curve The Keeling Curve is a graph of the accumulation of carbon dioxide in the Earth's atmosphere based on continuous measurements taken at the Mauna Loa Observatory on the island of Hawaii Hawaii ( ; haw, Hawaii ...


References


External links


Current global map of carbon dioxide concentrations in the atmosphereCurrent global map of the partial pressure of carbon dioxide at the ocean surfaceCurrent global map of the sea-air carbon dioxide flux density

Global Carbon Dioxide Circulation
(
NASA The National Aeronautics and Space Administration (NASA; ) is an independent agency A regulatory agency or regulatory authority, is a Public benefit corporation Public-benefit corporation is a term that has different meanings in differen ...

NASA
; 13 December 2016)
Video (03:10) – A Year in the Life of Earth's CO2
(
NASA The National Aeronautics and Space Administration (NASA; ) is an independent agency A regulatory agency or regulatory authority, is a Public benefit corporation Public-benefit corporation is a term that has different meanings in differen ...

NASA
; 17 November 2014) {{DEFAULTSORT:Carbon Dioxide In Earth's Atmosphere Atmosphere of Earth Carbon dioxide Greenhouse gases fr:Dioxyde de carbone#CO2 dans l'atmosphère terrestre