10:45 〜 11:00
[ACG35-07] Imprint of Fossil fuel uncertainty on posterior land CO2 fluxes
キーワード：MIROC4-ACTM inverson, Fossil Fuel CO2 emission uncertainty , Posterior land biospheric fluxes
The top-down inversion method, widely used to estimate land carbon fluxes (henceforth posterior land fluxes) from observed CO2 levels, hinges on near-perfect knowledge of fossil fuel consumption and cement production CO2 (FFC CO2) emissions. However, the uncertainty in the FFC emissions is considerable and varies significantly at regional and country scales. The recent GridFEDv2023.1 inventory underscores notable uncertainties in FFC emission increase rate during 2000s —a crucial period for many countries establishing baselines for Nationally Determined Contributions (NDCs) and net-zero emission targets. The oversights of FFC uncertainty can lead to inaccuracies in posterior carbon sinks as inversion balances FFC emissions with the residual/inversion sink estimation for simulating the global atmospheric burden increase. In this study, we investigate the impact of FFC emission uncertainty on the spatio-temporal estimate of posterior carbon flux for 2001-2022 using the MIROC4-ACTM-based inversion system.
The global land biosphere exhibited a marked increase in net carbon uptake from 2001 to 2011, followed by a phase of saturation and a weakening of the net carbon sink. The TRENDY Dynamic Global Vegetation Model (DGVM) ensemble simulations attributed these changes in land carbon sinks to climate variations and the stimulating effect of rising atmospheric CO2 on photosynthesis (CO2 fertilization) in the tropical region, as well as plant regrowth in the higher northern latitudes. However, TRENDY ensemble models do not support the large increasing rate of posterior land carbon sink (-2.12 PgC yr-1) during 2001-2011 based on commonly used FFC emissions (control case: gmFFC). Furthermore, sensitivity tests based on lower bounds of FFC emissions (glFFC = gmFFC – Uncertainty) indicate that the faster increasing rate in posterior net land carbon uptake is likely a result of overestimated FFC emission increase rates from 2001 to 2011. The primary source of uncertainty in the increased rate of FFC emissions arises from China, while significant systematic over/under-estimations are likely for the contiguous USA and Western Europe. The lower bound of FFC growth rate in China aligns the inversion-estimated global and China land-biospheric carbon sink increase with TRENDY model fluxes. The FFC uncertainty has minimal impacts on posterior ocean fluxes as fossil fuels are predominantly burned over land. These findings have broad implications for our understanding of the terrestrial ecosystem's capacity to support nature-based solutions in response to climate change.
Acknowledgement
We acknowledge the TRENDY project and participating modeling groups for the DGVM data.
TRENDY v11 gridded data, used in this study, were accessed by contacting Stephen Sitch.
The global land biosphere exhibited a marked increase in net carbon uptake from 2001 to 2011, followed by a phase of saturation and a weakening of the net carbon sink. The TRENDY Dynamic Global Vegetation Model (DGVM) ensemble simulations attributed these changes in land carbon sinks to climate variations and the stimulating effect of rising atmospheric CO2 on photosynthesis (CO2 fertilization) in the tropical region, as well as plant regrowth in the higher northern latitudes. However, TRENDY ensemble models do not support the large increasing rate of posterior land carbon sink (-2.12 PgC yr-1) during 2001-2011 based on commonly used FFC emissions (control case: gmFFC). Furthermore, sensitivity tests based on lower bounds of FFC emissions (glFFC = gmFFC – Uncertainty) indicate that the faster increasing rate in posterior net land carbon uptake is likely a result of overestimated FFC emission increase rates from 2001 to 2011. The primary source of uncertainty in the increased rate of FFC emissions arises from China, while significant systematic over/under-estimations are likely for the contiguous USA and Western Europe. The lower bound of FFC growth rate in China aligns the inversion-estimated global and China land-biospheric carbon sink increase with TRENDY model fluxes. The FFC uncertainty has minimal impacts on posterior ocean fluxes as fossil fuels are predominantly burned over land. These findings have broad implications for our understanding of the terrestrial ecosystem's capacity to support nature-based solutions in response to climate change.
Acknowledgement
We acknowledge the TRENDY project and participating modeling groups for the DGVM data.
TRENDY v11 gridded data, used in this study, were accessed by contacting Stephen Sitch.