Elevated CO2 concentrations increase photosynthesis and, potentially, net ecosystem production (NEP), meaning a greater CO2 uptake. Climate, nutrients and ecosystem structure, however, influence the effect of increasing CO2. Here we analysed global NEP from MACC-II and Jena CarboScope atmospheric inversions and ten dynamic global vegetation models (TRENDY), using statistical models to attribute the trends in NEP to its potential drivers: CO2, climatic variables and land-use change. We found that an increased CO2 was consistently associated with an increased NEP (1995–2014). Conversely, increased temperatures were negatively associated with NEP. Using the two atmospheric inversions and TRENDY, the estimated global sensitivities for CO2 were 6.0 ± 0.1, 8.1 ± 0.3 and 3.1 ± 0.1 PgC per 100 ppm (~1 °C increase), and −0.5 ± 0.2, −0.9 ± 0.4 and −1.1 ± 0.1 PgC °C−1 for temperature. These results indicate a positive CO2 effect on terrestrial C sinks that is constrained by climate warming.
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The authors declare that the data supporting the findings of this study are publicly available in the web pages provided in the article. The TRENDY simulations are available from the corresponding author upon request.
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This research was supported by the Spanish Government project CGL2016–79835-P (FERTWARM), the European Research Council Synergy grant no. ERC-2013-726 SyG-610028 IMBALANCE-P and the Catalan Government project SGR 2017–1005. M.F.-M. and S.V. are postdoctoral fellows of the Research Foundation—Flanders. J.G.C. thanks the support of the National Environmental Science Programme ESCC Hub. We thank C. Röedenbeck for his advice and for distributing Jena CarboScope and all the modellers that contributed to the TRENDY project.
The authors declare no competing interests.
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Fernández-Martínez, M., Sardans, J., Chevallier, F. et al. Global trends in carbon sinks and their relationships with CO2 and temperature. Nature Clim Change 9, 73–79 (2019) doi:10.1038/s41558-018-0367-7
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