Systematic anomalies in the recent global atmospheric CO2 concentration

What is it about?

The motivation for this study was to understand the highly systematic and uniform variation in observed annual CO2 concentrations throughout the Southern Hemisphere over the three decades since 1992. This marked the beginning of CSIRO monitoring of atmospheric CO2 and its isotopes with unprecedented measurement precision and, at the Cape Grim Observatory, with unparalleled verification of air mass history. Direct calculations have revealed that the annual variation in Southern Hemisphere CO2 data is dominated by the atmospheric flux of Northern Hemisphere fossil emissions. This contrasts with the widely assumed cause of being due to regional air-surface exchanges. Our PLOS study now shows how the large interhemispheric CO2 flux has significant volatility on sub-annual time frames. This, combined with sub-annual variability in inter-hemispheric partial pressure difference, is a critical and previously ignored factor in describing large scale background CO2 concentration variations. Conventional analyses, including complex numerical modelling of the global carbon cycle, have focussed on using growth rates to identify regional air-surface fluxes. Our study shows that the common method of summing those fluxes to get a global response, is an indirect and imprecise way of monitoring changes in the total mass of CO2 in the atmosphere, the determinant of anthropogenic in climate forcing and ocean acidification. The Cape Grim baseline-selected data provide this forcing in near real time.

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Photo by Caden Tormey on Unsplash

Photo by Caden Tormey on Unsplash

Why is it important?

Direct calculations have revealed that the annual variation in Southern Hemisphere CO2 data is dominated by the atmospheric flux of Northern Hemisphere fossil emissions. This contrasts with the widely assumed cause of being due to regional air-surface exchanges.

Perspectives