Investigating the differences in calculating global mean surface CO2 abundance: the impact of analysis methodologies and site selection Journal Article uri icon



  • Abstract. The World Meteorological Organization (WMO) Global Atmosphere Watch (GAW) coordinates high-quality atmospheric greenhouse gas observations globally and provides these observations through the WMO World Data Centre for Greenhouse Gases (WDCGG) supported by Japan Meteorological Agency. The WDCGG and the National Oceanic and Atmospheric Administration (NOAA) analyse these measurements using different methodologies and site selection to calculate global annual mean surface CO2 and its growth rate as a headline climate indicator. This study proposes a third hybrid method named semi-NOAA, which is used as an independent validation of the methods as described by NOAA and WDCGG. We apply the semi-NOAA to incorporate observations from most WMO GAW stations and 3D modelled CO2 fields from CarbonTracker Europe (CTE). We found that different observational networks (i.e., the NOAA, GAW, and CTE networks) and analysis methods result in differences in the calculated global surface CO2 mole fractions equivalent to the current atmospheric growth rate over a three-month period. However, the CO2 growth rate derived from these networks and CTE model output shows good agreement. Over the long-term period (40 years), both networks with and without continental sites exhibit the same trend in the growth rate (0.030 ± 0.002 ppm per year). However, a clear difference emerges in the short-term (one month) change of the growth rate. The network that includes continental sites improves the early detection of changes in biogenic emissions.;

publication date

  • June 23, 2023

has restriction

  • green

Date in CU Experts

  • July 5, 2023 4:34 AM

Full Author List

  • Wu Z; Vermeulen A; Sawa Y; Karstens U; Peters W; de Kok R; Lan X; Nagai Y; Ogi A; Tarasova O

author count

  • 10

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