Editing IPCC:AR6/WGI/Chapter-4 (section)

==== 4.4.2.2 Ocean and Land Carbon Flux ====

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Ocean carbon flux is both a key feature of the physical ocean in mitigating the rise of atmospheric CO <sub>2</sub> and a driver of changes in the ocean biosphere, including changes in ocean acidity. Based on results from CMIP6 models, we conclude that SSP2-4.5, SSP3-7.0, and SSP5-8.5 all clearly lead to increasing 10-, 20-, and 30-year trends in ocean carbon flux over the near term ( ''high confidence'' ) (Figure 4.16,). Increasing trends in ocean carbon flux are less obvious in the lower-emissions scenarios. Ensemble-mean trends in land carbon flux over the near term are generally increasing, but these are ''unlikely'' to be detected given a large component of terrestrial variability combined with model uncertainty. A more detailed assessment is in [[IPCC:Wg1:Chapter:Chapter-5|Chapter 5]] (Section 5.2.1).

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[[File:c66d3bddc357e3e3fa62bed9693f8209 IPCC_AR6_WGI_Figure_4_16.png]]

'''Figure''' '''4.16 |''' '''CMIP6 trends in ocean and land carbon flux for 10-year, 20-year, and 30-year periods ending in 2021–2040. (a)''' Ocean carbon flux. '''(b)''' Land carbon flux. Plotted are the 5–95% ranges across the ensembles of simulations, for five SSPs. The numbers at the top of the plots are the number of model simulations in each SSP ensemble. Units are PgC yr <sup>–1</sup> per decade. Further details on data sources and processing are available in the chapter data table (Table 4.SM.1).

In summary, it is ''likely'' that ocean carbon flux will increase in the near term under the higher emissions scenarios, while a large component of terrestrial variability makes it is ''unlikely'' that an increase in land carbon flux will be detected over this period.

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