Carbon dioxide

Atmosphere

As of 2004, the earth's atmosphere is about 0.038% by volume (380 µL/L or ppmv) or 0.053% by weight CO2. This represents about 2.7 × 1012 tonnes of CO2. Due to the greater land area, and therefore greater plant life, in the northern hemisphere as compared to the southern hemisphere, there is an annual fluctuation of about 5 µL/L, peaking in May and reaching a minimum in October at the end of the northern hemisphere growing season, when the quantity of biomass on the planet is greatest.

Related Topics:
As of 2004 - Earth's atmosphere - Ppmv - Tonnes - Biomass

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Despite its small concentration, CO2 is a very important component of Earth's atmosphere, because it absorbs infrared radiation and enhances the greenhouse effect.

Related Topics:
Infrared - Greenhouse effect

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The initial carbon dioxide in the atmosphere of the young Earth was produced by volcanic activity; this was essential for a warm and stable climate conducive to life. Volcanic activity now releases about 130 to 230 teragrams (145 million to 255 million short tons) of carbon dioxide each year. Volcanic releases are about 1% of the amount which is released by human activities.

Related Topics:
Volcanic activity - Teragrams - Short tons

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Since the start of the Industrial Revolution, the atmospheric CO2 concentration has increased by approximately 110 µL/L or about 40%, most of it released since 1945. Monthly measurements taken at Mauna Loa http://cdiac.esd.ornl.gov/trends/co2/sio-mlo.htm since 1958 show an increase from 316 µL/L in that year to 376 µL/L in 2003, an overall increase of 60 µL/L during the 44-year history of the measurements. Burning fossil fuels such as coal and petroleum is the leading cause of increased man-made CO2; deforestation the second major cause. In 1997, Indonesian peat fires may have released 13-40% as much carbon as fossil fuel burning does http://en.wikipedia.org/wiki/Peat#Peat_fires. Various techniques have been proposed for removing excess carbon dioxide from the atmosphere in carbon dioxide sinks.

Related Topics:
Industrial Revolution - 1945 - Mauna Loa - 1958 - 2003 - Fossil fuel - Coal - Petroleum - Deforestation - Peat - Carbon dioxide sink

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The Global Warming Theory (GWT) predicts that increased amounts of CO2 in the atmosphere tend to enhance the greenhouse effect and thus contribute to global warming. The effect of combustion-produced carbon dioxide on climate is called the Callendar effect.

Related Topics:
Greenhouse effect - Global warming - Callendar effect

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Variation in the past

The most direct method for measuring atmospheric carbon dioxide concentrations for periods before direct sampling is to measure bubbles of air (fluid or gas inclusions) trapped in the Antarctic or Greenland ice caps. The most widely accepted of such studies come from a variety of Antarctic cores and indicate that atmospheric CO2 levels were about 260–280µL/L immediately before industrial emissions began and did not vary much from this level during the preceding 10,000 years.

Related Topics:
Fluid or gas inclusions - Antarctic - Greenland

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The longest ice core record comes from Vostok, Antarctica, where ice has been sampled to a depth of 3,600 meters, corresponding to an age of 420,000 years before the present. http://cdiac.esd.ornl.gov/trends/co2/vostok.htm During this time, the atmospheric carbon dioxide concentration has varied between 180–210 µL/L during ice ages, increasing to 280–300 µL/L during warmer interglacials.

Related Topics:
Ice core - Vostok, Antarctica - Ice age - Interglacial

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Some studies have disputed the claim of stable CO2 levels during the present interglacial (the last 10 kyr). Based on an analysis of fossil leaves, Wagner et al.{{ref|Wagner2002}} argued that CO2 levels during the period 7-10 kyr ago were significantly higher (~300 µL/L) 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 CO2{{ref|Indermuhle1999}}. Relevant to this dispute is the observation that Greenland ice cores often report higher and more variable CO2 values than similar measurements in Antarctica. However, the groups responsible for such measurments (e.g. Smith et al.{{ref|Smith1997}}) believe the variations in Greenland cores result from in situ decomposition of calcium carbonate dust found in the ice. When dust levels in Greenland cores are low, as they nearly always are in Antarctic cores, the researchers report good agreement between Antarctic and Greenland CO2 measurements.

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On longer time scales, various proxy measurements have been used to attempt to determine atmospheric carbon dioxide levels millions of years in the past. These include boron and carbon isotope ratios in certain types of marine sediments, and the number of stomata observed on fossil plant leaves. While these measurements give much less precise estimates of carbon dioxide concentration than ice cores, there is evidence for very high CO2 concentrations (>3,000 µL/L) between 600 and 400 Myr BP and between 200 and 150 Myr BP.http://www.grida.no/climate/ipcc_tar/wg1/fig3-2.htm On long time-scales, atmospheric CO2 content is determined by the balance among geochemical processes including organic carbon burial in sediments, silicate rock weathering, and vulcanism. The net effect of slight imbalances in the carbon cycle over tens to hundreds of millions of years has been to reduce atmospheric CO2. The rates of these processes are extremely slow, hence they are of limited relevance to the atmospheric CO2 response to emissions over the next hundred years. In more recent times, atmospheric CO2 concentration continued to fall after about 60 Myr BP and there is geochemical evidence that concentrations were

Related Topics:
Boron - Carbon - Isotope - Stomata - Weathering - C4

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