Surprising stability of recent global carbon cycling enables improved fossil fuel emission verification

The interannual to decadal variability in natural carbon sinks limits the explanation of recent changes in atmospheric CO2 concentration. Here we account for interannual and decadal variability using a simple quasi-mechanistic model of the net land carbon exchange with terms scaling with atmospheric CO2 and a weighted spatial average of temperature anomalies. This approach reduces the unexplained residual in Earth's carbon cycle budget from ±0.76 GtC per year obtained using process models to ±0.50 GtC per year, with the largest improvements on decadal timescales despite assuming constant dynamics. Our findings reveal remarkable stability of the carbon cycle and allow verification of reported global emissions to within 4.4% (95% confidence level) over the five-year stocktake cycle of the Paris Agreement—half the uncertainty reported previously.

Benjamin Birner, Christian Rödenbeck, Julia L. Dohner, Armin Schwartzman, Ralph F. Keeling