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Biogeosciences An interactive open-access journal of the European Geosciences Union
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Volume 13, issue 3
Biogeosciences, 13, 873–885, 2016
https://doi.org/10.5194/bg-13-873-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 13, 873–885, 2016
https://doi.org/10.5194/bg-13-873-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 17 Feb 2016

Research article | 17 Feb 2016

The 2009–2010 step in atmospheric CO2 interhemispheric difference

R. J. Francey and J. S. Frederiksen R. J. Francey and J. S. Frederiksen
  • CSIRO Oceans & Atmosphere, Aspendale, Victoria, Australia

Abstract. The annual average CO2 difference between baseline data from Mauna Loa and the Southern Hemisphere increased by  ∼  0.8 µmol mol−1 (0.8 ppm) between 2009 and 2010, a step unprecedented in over 50 years of reliable data. We find no evidence for coinciding, sufficiently large source and sink changes. A statistical anomaly is unlikely due to the highly systematic nature of the variation in observations. An explanation for the step, and the subsequent 5-year stability in this north–south difference, involves interhemispheric atmospheric exchange variation. The selected data describing this episode provide a critical test for studies that employ atmospheric transport models to interpret global carbon budgets and inform management of anthropogenic emissions.

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A step in the annual average CO2 difference between Mauna Loa and the Southern Hemisphere of 0.8 ppm in 2009–2010 has no precedence in 50 years. Variations in interhemispheric exchange coincide with the step, the subsequent 5-year north-south CO2 stability, and historic differences. This behaviour provides a critical test for studies that employ atmospheric transport models to interpret global carbon budgets and inform management of anthropogenic emissions.
A step in the annual average CO2 difference between Mauna Loa and the Southern Hemisphere of 0.8...
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