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Climate and Atmosphere -- Global Gas Concentrations: CO2Provided by the World Resources Institute (http://www.wri.org)Units: Parts per million

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20082007200620052004200320022001200019991998199719961995199419931992199119901989198819871986198519841983198219811980197919781977197619751974197319721971197019691968196719661965196319621961196019591953194319351927192119151909190519031899188718781874186918541847184318391816179117641744

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World385.34383.55381.84379.67377.38375.64373.1371.02369.48368.31366.63363.76362.64360.88358.89357.04356.37355.59354.19352.91351.48348.93347.15345.9344.42342.78341.13339.93338.69336.85335.51333.9332.15331.15330.25329.68327.45326.32325.68324.63323.05322.16321.38320.04318.99318.45317.64316.91315.98312.7307.9306.6305.5301.6300.5299.2296.9294.8295.8292.3290.3289.5289.3288.2286.8287.4283.1283.8279.7276.7276.8

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Footnotes

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1 -- World

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Data after 1958 are from Mauna Loa Observatory

Data before 1958 are from the Siple Ice Core.

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Source

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Data before 1958: Neftel, Friedli, Moore et al. 1994. Historical Carbon Dioxide Record from the Siple Station Ice Core (reported on-line by the Carbon Dioxide Information Analysis Center at http://cdiac.esd.ornl.gov/ftp/trends/co2/siple2.013). Bern, Switzerland: University of Bern.

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Data after 1958: Keeling, C.D., Whorf, T.P., and the Scripps Institute of Oceanography. 2005. Atmospheric CO2 Concentrations (ppmv) derived from in-situ air samples collected at Mauna Loa Observatory, Hawaii (reported on-line by the Carbon Dioxide Information Analysis Center at http://cdiac.ornl.gov/ftp/trends/co2/maunaloa.co2. Mauna Loa: Scripps Institute of Oceanography.

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Technical Notes

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Definition:

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The concentration of carbon dioxide (CO2) is the average mole fraction of CO2 in water-vapor-free air. Concentrations are measured in parts per million by volume (ppmv).

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Years Covered and Frequency of Update:

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Historical (pre-industrial) carbon dioxide estimates begin in 1744 and are available for 22 different years between 1744 and 1953. The data were initially published in 1986.

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Data from the Mauna Loa observatory have been reported from 1958 to 2005. While EarthTrends reports annual averages, the Mauna Loa data are recorded monthly, except for a few interruptions. CDIAC updates the Mauna Loa dataset on their website at least once a year; data for 2004 were posted on CDIAC’s website in May 2005.

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Methodology:

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The preindustrial concentrations of carbon dioxide were estimated by measuring CO2 concentrations of air enclosed in an ice core at Siple Station, Antarctica. The age of the the air trapped in the sample is estimated based on the depth of the core measurement and the age of the surrounding ice.

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The post-1959 data presented here are from the Scripps Institution of Oceanography in Mauna Loa, Hawaii (19 degrees 32 minutes North latitude, 155 degrees 35 minutes West longitude). The Mauna Loa dataset is the longest continuous record of atmospheric CO2 concentrations in the world. In years where one monthly value is missing, annual values were calculated by substituting a fit value (4-harmonics with gain factor and spline) for that month and then averaging the twelve monthly values.

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Details concerning data collection, revisions, and analysis are contained in C.D. Keeling, et al., Measurement of the Concentration of Carbon Dioxide at Mauna Loa Observatory, Hawaii, in W.C. Clark, ed., Carbon Dioxide Review: 1982 (Oxford University Press, New York, 1982).

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Data Reliability:

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The carbon dioxide measurements presented here reflect global trends. However, it is important to note that CO2 concentrations differ significantly among monitoring sites at any given time. The data presented here in EarthTrends are specific to the locations where the measurements were taken and are not global averages. For example, the average annual concentration at the South Pole in 1997 was 2.3 parts per million lower than at Mauna Loa. Annual means disguise large daily and seasonal variations in CO2 concentrations. During the summer, photosynthetic plants store larger amounts of carbon than in the winter, resulting in seasonal variation in measurements.

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The data from the Mauna Loa station reflect very precise measurements. Data are revised to correct for drift in instrument calibration, hardware changes, and perturbations to "background" conditions. Early in the data series, some CO2 measurements are missing for up to 3 consecutive months; for these series, annual mean figures were derived using interpolated data.

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The measurements of pre-industrial CO2 concentrations are estimates and not as reliable as current measurements from Mauna Loa. However, numerous groups have arrived at very similar CO2 concentration measurements using air trapped in ice cores taken from the Siple Station. In addition, the data agree with measurements of CO2 in ice cores taken at other sites, such as the Law Dome Ice Core, also in Antarctica.