2:15 PM - 2:30 PM
[AOS13-03] Weaker than expected future ocean carbon uptake due to carbon-climate feedbacks
Keywords:ocean carbon uptake, terrestrial carbon uptake, Earth System Model, emission-driven
The global ocean and terrestrial carbon dioxide (CO2) sinks have removed approximately half of the total anthropogenic emissions emitted to the atmosphere since 1850. Robust estimates of future carbon uptake are paramount to determine Paris Agreement compatible remaining greenhouse gas emission budgets including negative emission pathways to balance hard to abate emissions. However, carbon-climate feedbacks are usually excluded in state-of-the-art greenhouse gas concentration-driven Earth System Model (ESMs) experiments. Here, historical and future carbon uptake estimates from emission-driven CMIP6 experiments conducted with AWI-ESM-1-REcoM are presented.
Before the 1970s, carbon-climate feedbacks and differences in the initial distribution of terrestrial vegetation lead to a reduced carbon source from anthropogenic land use changes, a smaller atmospheric CO2 growth and a substantially weaker oceanic and terrestrial carbon uptake increase in the emission- versus concentration-driven model setup. Thereafter, the terrestrial CO2 sink increases stronger in the emission-driven setup, compensating for increased fossil fuel burning emissions and leading to similar atmospheric CO2 growth in both model setups. By the end of the 21st century, these carbon-climate feedbacks yield atmospheric CO2 concentrations considerably lower by 28 to 53 ppm and a weaker ocean CO2 sink in the emission-driven model setup, with the largest differences in strong mitigation scenarios. As emission-driven ESM setups are recommended for the upcoming CMIP7, these model results stress the need to improve our understanding of the future evolution of the global carbon sinks.
Before the 1970s, carbon-climate feedbacks and differences in the initial distribution of terrestrial vegetation lead to a reduced carbon source from anthropogenic land use changes, a smaller atmospheric CO2 growth and a substantially weaker oceanic and terrestrial carbon uptake increase in the emission- versus concentration-driven model setup. Thereafter, the terrestrial CO2 sink increases stronger in the emission-driven setup, compensating for increased fossil fuel burning emissions and leading to similar atmospheric CO2 growth in both model setups. By the end of the 21st century, these carbon-climate feedbacks yield atmospheric CO2 concentrations considerably lower by 28 to 53 ppm and a weaker ocean CO2 sink in the emission-driven model setup, with the largest differences in strong mitigation scenarios. As emission-driven ESM setups are recommended for the upcoming CMIP7, these model results stress the need to improve our understanding of the future evolution of the global carbon sinks.