National CO<sub>2</sub> budgets (2015–2020) inferred from atmospheric CO<sub>2</sub> observations in support of the global stocktake

oleh: B. Byrne, D. F. Baker, S. Basu, S. Basu, M. Bertolacci, K. W. Bowman, K. W. Bowman, D. Carroll, D. Carroll, A. Chatterjee, F. Chevallier, P. Ciais, N. Cressie, N. Cressie, D. Crisp, S. Crowell, F. Deng, Z. Deng, N. M. Deutscher, M. K. Dubey, S. Feng, O. E. García, D. W. T. Griffith, B. Herkommer, L. Hu, A. R. Jacobson, A. R. Jacobson, R. Janardanan, S. Jeong, M. S. Johnson, D. B. A. Jones, R. Kivi, J. Liu, J. Liu, Z. Liu, S. Maksyutov, J. B. Miller, S. M. Miller, I. Morino, J. Notholt, T. Oda, T. Oda, C. W. O'Dell, Y.-S. Oh, H. Ohyama, P. K. Patra, H. Peiro, C. Petri, S. Philip, D. F. Pollard, B. Poulter, M. Remaud, A. Schuh, M. K. Sha, K. Shiomi, K. Strong, C. Sweeney, Y. Té, H. Tian, H. Tian, V. A. Velazco, V. A. Velazco, M. Vrekoussis, M. Vrekoussis, T. Warneke, J. R. Worden, D. Wunch, Y. Yao, J. Yun, A. Zammit-Mangion, N. Zeng, N. Zeng

Format: Article
Diterbitkan: Copernicus Publications 2023-03-01

Deskripsi

<p>Accurate accounting of emissions and removals of CO<span class="inline-formula"><sub>2</sub></span> is critical for the planning and verification of emission reduction targets in support of the Paris Agreement. Here, we present a pilot dataset of country-specific net carbon exchange (NCE; fossil plus terrestrial ecosystem fluxes) and terrestrial carbon stock changes aimed at informing countries' carbon budgets. These estimates are based on “top-down” NCE outputs from the v10 Orbiting Carbon Observatory (OCO-2) modeling intercomparison project (MIP), wherein an ensemble of inverse modeling groups conducted standardized experiments assimilating OCO-2 column-averaged dry-air mole fraction (<span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M5" display="inline" overflow="scroll" dspmath="mathml"><mrow><msub><mi>X</mi><mrow><msub><mi mathvariant="normal">CO</mi><mn mathvariant="normal">2</mn></msub></mrow></msub></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="25pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="ffa38be111dbfeee63825a71ce00a601"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="essd-15-963-2023-ie00001.svg" width="25pt" height="14pt" src="essd-15-963-2023-ie00001.png"/></svg:svg></span></span>) retrievals (ACOS v10), in situ CO<span class="inline-formula"><sub>2</sub></span> measurements or combinations of these data. The v10 OCO-2 MIP NCE estimates are combined with “bottom-up” estimates of fossil fuel emissions and lateral carbon fluxes to estimate changes in terrestrial carbon stocks, which are impacted by anthropogenic and natural drivers. These flux and stock change estimates are reported annually (2015–2020) as both a global 1<span class="inline-formula"><sup>∘</sup></span> <span class="inline-formula">×</span> 1<span class="inline-formula"><sup>∘</sup></span> gridded dataset and a country-level dataset and are available for download from the Committee on Earth Observation Satellites' (CEOS) website: <a href="https://doi.org/10.48588/npf6-sw92">https://doi.org/10.48588/npf6-sw92</a> <span class="cit" id="xref_paren.1">(<a href="#bib1.bibx24">Byrne et al.</a>, <a href="#bib1.bibx24">2022</a>)</span>. Across the v10 OCO-2 MIP experiments, we obtain increases in the ensemble median terrestrial carbon stocks of 3.29–4.58 <span class="inline-formula">Pg CO<sub>2</sub> yr<sup>−1</sup></span> (0.90–1.25 <span class="inline-formula">Pg C yr<sup>−1</sup></span>). This is a result of broad increases in terrestrial carbon stocks across the northern extratropics, while the tropics generally have stock losses but with considerable regional variability and differences between v10 OCO-2 MIP experiments. We discuss the state of the science for tracking emissions and removals using top-down methods, including current limitations and future developments towards top-down monitoring and verification systems.</p>