3:45 PM - 4:00 PM
[ACG09-08] Current state of terrestrial CO2 exchange estimations: progresses and remaining issues
Keywords:Terrestrial CO2 exchange, Atmospheric CO2 inversion, Ecosystem model simulation
However, the current estimates of terrestrial CO2 exchange by the bottom-up and top-down approaches remain inconsistent. As illustrated in the recent IPCC Assessment Report (AR5), the top-down approach tends to indicate stronger CO2 sinks in temperate and boreal regions than the bottom-up approach does. Furthermore, the two approaches exhibited contrasting CO2 sink–source patterns in the tropics; the bottom-up approach indicated CO2 sinks and the top-down approach CO2 sources. As illustrated by these inconsistencies, a consensus on the geographic distribution of the terrestrial CO2 exchange has yet to be established among the research community.
In this study, we elaborate the current status and issues of terrestrial CO2 flux estimations by the top-down and bottom-up approaches. Specifically, we compare the bottom-up estimate from dynamic global vegetation models that are forced by interannual variations of CO2 concentration, climate and land use changes, with the top-down estimate from atmospheric CO2 inversions. We show an improved level of agreement between the two estimates in relation to seasonal variability and, regional and global budgets, since the IPCC AR5. We also discuss the remaining issues causing inconsistency between the two estimates.
This research was supported by Environment Research and Technology Development Funds (2-1401) from the Ministry of the Environment of Japan and Asia-Pacific Network for Global Change Research (APN: grant#ARCP2011-11NMY-Patra/Canadell).