[A-AS04] [EE] Global Carbon Cycle Observation and Analysis

[AAS04-10] Implications of overestimated anthropogenic CO₂ emissions on East Asian CO₂ sources and sinks estimations

*Tazu Saeki¹, Prabir K. Patra¹ (1.Japan Agency for Marine-Earth Science and Technology)

Keywords:East Asian Carbon Budget, Fossil Fuel Emission, Terrestrial Biospheric Uptake

Measurement and modelling of regional or country-level carbon dioxide (CO₂) fluxes are becoming critical for verification of the greenhouse gases emission control. One of the commonly adopted approaches is inverse modelling, where CO₂ fluxes (emission: positive flux, sink: negative flux) from the terrestrial ecosystems are estimated by combining atmospheric CO₂ measurements with atmospheric transport models. The inverse models assume anthropogenic emissions are known, and thus the uncertainties in the emissions introduce systematic bias in estimation of the terrestrial (residual) fluxes by inverse modelling. Here we show that the CO₂ sink increase, estimated by the inverse model, over East Asia (China, Japan, Korea and Mongolia), by about 0.26 PgC yr^-1 (1 Pg = 10¹² g) during 2001-2010, is suggested as an artifact of the anthropogenic CO₂ emissions increasing too quickly in China by 1.41 PgC yr^-1. Independent results from methane (CH₄) inversion suggested about 41% lower rate of East Asian CH₄ emission increase during 2002-2012. We apply a scaling factor of 0.59, based on CH₄ inversion, to the rate of anthropogenic CO₂ emission increase since the anthropogenic emissions of both CO₂ and CH₄ increase linearly in the emission inventory. We find no systematic increase in land CO₂ uptake over East Asia during 1993-2010 or 2000-2009 when scaled anthropogenic CO₂ emissions are used, and that there is a need of higher emission increase rate for 2010-2012 compared to those calculated by the inventory methods. High bias in anthropogenic CO₂ emissions leads to stronger land sinks in global land-ocean flux partitioning in our inverse model. The corrected anthropogenic CO₂ emissions also produce measurable reductions in the rate of global land CO₂ sink increase post-2002, leading to a better agreement with the terrestrial biospheric model simulations that include CO₂-fertlization and climate effects.