Whole-atmospheric monthly CO2 concentration tops 400 ppm- Preliminary GOSAT monitoring results May 20, 2016
Ministry of the Environment, Japan
National Institute for Environmental Studies
Japan Aerospace Exploration Agency
The Ministry of the Environment, Japan (MOEJ), National Institute for Environmental Studies(NIES), and Japan Aerospace Exploration Agency (JAXA) have been monitoring carbon dioxide (CO2)and methane (CH4) by the Greenhouse gases Observing SATellite "IBUKI" (GOSAT).
A recent provisional analysis of GOSAT observational data shows that the global atmospheric monthly
mean CO2 concentration observed vertically through the whole atmosphere exceeded 400 ppm in
December 2015 for the first time since GOSAT was launched in 2009.
● Whole-atmospheric monthly mean CO2 concentrations as seen by GOSAT
The three parties - Ministry of the Environment, Japan (MOEJ), National Institute for EnvironmentalStudies (NIES), and Japan Aerospace Exploration Agency (JAXA) - have published thewhole-atmospheric monthly mean CO2 concentrations (observations made vertically through the wholeatmosphere) analyzed and estimated from GOSAT observations from May 2009 to January 2016, and thetrend line of the global CO2 mean (average seasonal cycle removed) on the website: NIES GOSAT Project"Whole-atmospheric monthly mean CO2 concentrations"(http://www.gosat.nies.go.jp/en/recent-global-co2.html).
According to a provisional analysis (until January 2016), the monthly mean concentration exceeded 400
ppm for the first time and it recorded 400.2 ppm in December 2015. It also recorded 401.1 ppm in January
2016, and it is observed that the concentration has increased in winter towards spring in the NorthernHemisphere (see the figure).
Several meteorological agencies such as the World Meteorological Organization (WMO) have alreadyreported that the global monthly mean CO2 concentration based on data obtained at surface-levelmonitoring sites has exceeded 400 ppm. However, it is the first time that the whole-atmospheric CO2mean exceeded 400 ppm monitored by GOSAT, which can observe CO2 concentrations from the surface
to the top of the atmosphere (about 70km). It means that CO2 concentrations are increasing not only at theglobal surface but also in the global atmosphere.
The trend line of the global CO2 mean reached 399.6 ppm in January 2016, and if this increasing trend
continues, it will probably be found upon more careful analysis that the trend line has exceeded 400 ppm
around March 2016. It means that current global atmospheric CO2 concentrations substantially exceed 400ppm.
These results are based on a preliminary analysis of the systematic bias of GOSAT. For more
information about the analysis method and explanation, please see the below-mentioned website:"Whole-atmosphere monthly mean CO2 concentration"(http://www.gosat.nies.go.jp/en/recent-global-co2.html). An explanatory document (PDF) will beavailable soon on the website.
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Whole-atmospheric CO2 concentrations monitored by GOSAT: monthly mean () and trend ().

The three parties will continue the public dissemination of new findings from GOSAT observations.
Also, the parties plan to continue the ongoing space-based greenhouse gas observation with the GOSAT
successor GOSAT-2, which is planned to be launched in the Japanese fiscal year 2017. The results of thecontinued observation will be utilized for the elaboration and refinement of global warming predictions.
[Acknowledgement]
For the analysis of GOSAT observational data, two weather analysis datasets were used: GPV (Grid PointValue) data provided by the Japan Meteorological Agency and JCDAS data generated in the JRA-25
long-term reanalysis project by the Japan Meteorological Agency and the Central Research Institute ofElectric Power Industry.
[Contact Information]
About GOSAT data and analysis results:
NIES Satellite Observation Center, GOSAT Project
Phone: +81-29-850-2966
About GOSAT, onboard sensors, and observation status:
Masakatsu Nakajima
JAXA Space Technology Directorate I
GOSAT-2 Project Team
Phone: +81-50-3362-6130
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