12/07/2015

Large Divergence of Satellite and Earth System Model Estimates of Global Terrestrial CO2 Fertilization

Summary

Atmospheric mass balance analyses suggest that terrestrial carbon storage is increasing, partially abating the atmospheric carbon dioxide (CO₂) growth rate, although the continued strength of this ecosystem service remains uncertain. This research presents a new, satellite-derived global terrestrial Net Primary Production (NNP) dataset, which shows a significant increase in NPP from 1982 to 2011. However, comparison against Earth system model (ESM) estimates reveals a significant divergence, with satellite-derived increases (2.8 ± 1.5%) less than half of ESM-derived increases (7.60 ± 1.67%) over the 30-year period. By isolating the CO₂ fertilization effect and comparing against a synthesis of available free-air CO₂ enrichment data, the researchers provide evidence that much of the discrepancy may be due to an over-sensitivity of ESMs to atmospheric CO₂, potentially reflecting an under-representation of climatic feedbacks and a lack of representation of nutrient constraints. Understanding of CO₂ fertilization effects on NPP needs rapid improvement to enable more accurate projections of future carbon cycle-climate feedbacks. The study suggests that better integration of modeling, satellite, and experimental approaches offers a promising way forward.

References

Smith, W. K., S. C. Reed, C. C. Cleveland, A. P. Ballantyne,W. R. L. Anderegg, W. R.Wieder, Y. Y. Liu, and S. W. Running. 2015 “Large Divergence of Satellite and Earth System Model Estimates of Global Terrestrial CO₂ Fertilization,” Nature Climate Change 6, 306-10. DOI: 10.1038/nclimate2879.