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Abstract The global air‐sea CO2flux (F) impacts and is impacted by a plethora of climate‐related processes operating at multiple time scales. In bulk mass transfer formulations, F is driven by physico‐ and bio‐chemical factors such as the air‐sea partial pressure difference (∆pCO2), gas transfer velocity, sea surface temperature, and salinity–all varying at multiple time scales. To de‐convolve the impact of these factors on variability in F at different time scales, time‐resolved estimates of F were computed using a global data set assembled between 1988 and 2015. The F anomalies were defined as temporal deviations from the 28‐year time‐averaged value. Spectral analysis revealed four dominant timescales of variability in F–subseasonal, seasonal, interannual, and decadal with relative amplitude differences varying across regions. A second‐order Taylor series expansion was then conducted along these four timescales to separate drivers across differing regions. The analysis showed that on subseasonal timescales, wind speed variability explains some 66% of the global F anomaly and is the dominant driver. On seasonal, interannual, and decadal timescales, the ∆pCO2effect controlled by the ∆pCO2anomaly, explained much of the F anomaly. On decadal timescales, the F anomaly was almost entirely governed by the ∆pCO2effect with large contributions from high latitudes. The main drivers across timescales also dominate the regional F anomaly, particularly in the mid‐high latitude regions. Finally, the driver of the ∆pCO2effect was closely connected with the relative strength of atmospheric pCO2and the nonthermal component of oceanic pCO2anomaly associated with dissolved inorganic carbon and alkalinity.
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Surprising stability of recent global carbon cycling enables improved fossil fuel emission verification
Abstract The interannual to decadal variability in natural carbon sinks limits the explanation of recent changes in atmospheric CO2concentration. 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 CO2and 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.
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- Award ID(s):
- 1922922
- PAR ID:
- 10442546
- Publisher / Repository:
- Nature Publishing Group
- Date Published:
- Journal Name:
- Nature Climate Change
- Volume:
- 13
- Issue:
- 9
- ISSN:
- 1758-678X
- Page Range / eLocation ID:
- p. 961-966
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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