Greenhouse gases observing satellite GOSAT  "IBUKI"

Recent Global CO2


Whole-atmosphere monthly mean CO2 concentration based on GOSAT observations

- Recent data -

 Monthly mean CO2

 August 2016

400.7 ppm


 August 2016

401.7 ppm

 CO2 growth in the past one year (**)

 August 2016 - August 2015

2.9 ppm/yr

)   CO2 trend is a value on the CO2 trend line derived by removing averaged seasonal fluctuations from the

     monthly CO2 time series. Please note that with a new addition of monthly mean CO2 data, seasonal

     fluctuations may vary. Accordingly, past CO2 trend values can also change slightly.

**) CO2 growth refers to an increase of CO2 level on the trend line in the last one year.

Showing monthly mean GHG concentrations - global distribution and variations

Whole-atmosphere monthly mean carbon dioxide concentration

The project of the Greenhouse gases Observing SATellite "IBUKI" (GOSAT), the world’s first satellite designed specifically for monitoring greenhouse gases from space, is jointly promoted by the Ministry of the Environment, Japan, the National Institute for Environmental Studies, and Japan Aerospace Exploration Agency. The satellite has been in operation since its launch on January 23, 2009.


The above chart demonstrates the whole-atmosphere monthly mean concentration of carbon dioxide (CO2), calculated by using GOSAT data that reflect CO2 levels in all layers of the atmosphere. It is also showing seasonal oscillation and yearly rise over the analyzed period. It is also confirmed that the trend line of the whole-atmosphere CO2 mean (average seasonal cycle removed) increases monotonously. The value and the growth of the trend line are important to discuss global warming issues.


Characteristics and significance of greenhouse gas observation by GOSAT


CO2 changes at surface-level monitoring sites and the global CO2 mean based on those observations have long been reported by the World Meteorological Organization and several other meteorological agencies around the world. To further facilitate an understanding of overall trends for CO2 in the atmosphere, knowledge of “whole-atmosphere” CO2 mean is necessary, and for this, more CO2 information in the vertical direction is needed. In fact, from past measurements taken by aircraft, CO2 levels are known to vary with altitude. Model predictions of whole-atmosphere CO2 mean have appeared in the fifth assessment report by the Intergovernmental Panel on Climate Change, as they are important for predicting the risk of global warming due to rising greenhouse gas levels. This is where CO2 observation by GOSAT comes in useful, as the satellite measurement encompasses levels from the surface to the top of the atmosphere and provides CO2 concentration averaged over an entire atmospheric column (this is referred to as column-averaged CO2 concentration).



Whole-atmosphere monthly mean CO2 concentration based on GOSAT data


The whole-atmosphere mean CO2 concentration was calculated based on GOSAT measurement. Observational data collected by the satellite over a period exceeding six years since May 2009 were used for this calculation. Over the analyzed period, the monthly mean CO2 concentration continually rose, with seasonal fluctuations due to photosynthetic activity by plants that intensifies and subsides over a single year in the Northern Hemisphere. The trend line of the global CO2 mean, obtained by subtracting averaged seasonal fluctuations from the monthly CO2 time series, increases monotonously 1). We note here that areas that GOSAT measurement can cover are limited to parts of the globe without cloud cover and where the local solar altitude is above a specific threshold. Therefore, the global distribution of column-averaged CO2 concentration, needed for the calculation of the whole-atmosphere mean CO2 concentration, was estimated from GOSAT data 2). Shown in the figure above are the time series of the monthly mean CO2 concentration and the trend line calculated from the monthly time series 3). The values shown here are found to be smaller by 1-2 ppm than those based on CO2 measurements at the surface level 4).



Characteristics shown in the graph


According to a provisional analysis (until May 2016), the global atmospheric monthly mean CO2 concentration observed vertically through the whole atmosphere exceeded 400 ppm for the first time since GOSAT was launched in 2009 and it recorded 400.2 ppm in December 2015. Since then, through the winter to spring season in the Northern Hemisphere, a continued increase was observed until May 2016.


Further,the trend of the whole-atmospheric CO2 mean first exceeded 400 ppm in February 2016 with a peak value of 400.2 ppm. It means that current global atmospheric CO2 concentrations substantially exceed 400 ppm.






1)  Some of the GOSAT data used in this analysis, dated after February 2015, are still preliminary, pending final validation. The thermoelectric cooler (cryo-cooler) installed on the observation instrument aboard the satellite (TANSO-FTS) failed on August 2, 2015 and was restarted on September 14. Thus, for the computation of the whole-atmosphere mean CO2 and the CO2 trend for the months of August and September, we used the following versions of the GOSAT CO2 concentration data  that reflects changes in the characteristics of the observation instrument: ver. 02.50 (between Aug. 2 and Sep. 13); ver. 02.60 (after Sep. 15).

2)  More details on the estimation approach used here will be found at the following link soon.

3)  Result for January 2015 is missing due to lacking data for instrument adjustment.

4)  US National Oceanic and Atmospheric Administration reported that global mean CO2 concentration based on surface level measurements reached 400   ppm in March 2015. Source: reached-.aspx






[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






The GOSAT Project is a joint effort of the Ministry of the Environment (MOE), the National Institute for Environmental Studies (NIES), and the Japan Aerospace Exploration Agency (JAXA)

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