Editing IPCC:AR6/WGI/Chapter-3 (section)

=== Human Influence on the Biosphere ===

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'''The main driver of the observed increase in the amplitude of the seasonal cycle of atmospheric CO''' <sub>2</sub> '''is enhanced fertilization of plant growth by the increasing concentration of atmospheric CO''' <sub>2</sub> '''(''' medium confidence) '''.''' However, there is only ''low confidence'' that this CO <sub>2</sub> fertilization has also been the main driver of observed greening because land management is the dominating factor in some regions. Earth system models simulate globally averaged land carbon sinks within the range of observation-based estimates ( ''high confidence'' ), but global-scale agreement masks large regional disagreements. {3.6.1}

'''It is''' virtually certain '''that the uptake of anthropogenic CO''' <sub>2</sub> '''was the main driver of the observed acidification of the global''' '''surface open ocean.''' The observed increase in CO <sub>2</sub> concentration in the subtropical and equatorial North Atlantic since 2000 is ''likely'' associated in part with an increase in ocean temperature, a response that is consistent with the expected weakening of the ocean carbon sink with warming. Consistent with AR5 there is ''medium confidence'' that deoxygenation in the upper ocean is due in part to human influence. There is ''high confidence'' that Earth system models simulate a realistic time evolution of the global mean ocean carbon sink. {3.6.2}

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