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Carbon Dioxide (CO2)

   Among greenhouse gases, carbon dioxide (CO2) is the most significant contributor to global warming. Its atmospheric concentration has increased in recent times as a result of emissions from various human activities such as fossil-fuel combustion, cement production and deforestation. Among these activities, the combustion of fossil fuels accounts for about three quarters of all anthropogenic CO2 emissions. The results of WDCGG analysis show that the global mean annual atmospheric CO2 mole fraction was 403.3 ppm in 2016, an increase of 3.3 ppm from the previous year. This is 45% higher than the pre-industrial level (278 ppm). 


JMA Observation

   JMA observes surface concentrations of CO2 at three stations in Japan.
   The upper panel of the figures below shows a time-series representation of CO2 mole fractions at these stations. In all data, values vary with a seasonal cycle in relation to photosynthesis and respiration in the biosphere. The mole fraction at Ryori has larger seasonal variations than those at the other two stations because the station is located at a higher latitude, where the atmosphere is significantly influenced by biospheric activity. The values are generally higher at Yonagunijima than those at Minamitorishima despite the almost identical latitudes of the two locations. This reflects the influence of anthropogenic and wintertime biospheric emissions from the Asian continent.
   The increases in CO2 mole fractions at all three stations show almost simultaneous variations, as seen in the lower panel of the figure below. It is well known that annual variations in CO2 mole fractions are related to the El Niño-Southern Oscillation; the El Niño events in 1986-1988, 1997/1998, 2002/2003, 2009/2010 and 2014-2016 coincided with high growth rates of CO2.

Time-series representation of CO2 mole fractions and growth rates recorded at JMA observatories

Time-series representation of CO2 mole fractions and growth rates recorded at JMA observatories
Provisional values are included.

Globally averaged mole fractions

   The figure below shows a time-series representation of globally averaged CO2 mole fractions as analyzed by the WDCGG using statistical methods.
   The increase observed in the values corresponds to the results of JMA observations.

Time-series representation of globally averaged CO2 mole fractions

Time-series representation of globally averaged CO2 mole fractions
Blue: monthly mean mole fractions. Red: monthly mean with seasonal variations removed.

Zonally averaged mole fractions

   The figure below shows variations in zonally averaged atmospheric CO2 mole fractions analyzed using data submitted to the WDCGG from fixed stations and some ships. The values are high in mid and high latitudes of the Northern Hemisphere, and decrease toward southerly latitudes. This latitudinal distribution of CO2 mole fractions suggests that major CO2 sources are located in the mid and high latitudes of the Northern Hemisphere.  The seasonal variation (a decrease from spring to summer and an increase from summer to spring) is mainly characterized by the activity of the terrestrial biosphere, and its amplitude in the Southern Hemisphere is smaller than that in the Northern Hemisphere due to the smaller land area of the former. In both hemispheres, atmospheric CO2 mole fractions increase year by year.

Time-series representation of zonally averaged CO2 mole fractions

Time-series representation of zonally averaged CO2 mole fractions

CO2 distribution

   The results of JMA's global CO2 distribution analysis can be accessed at "Carbon Dioxide (CO2) Distribution".

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