Fig. 2.

Schematic representation of how carbon flows among atmospheric, land, ocean, and geological reservoirs may change due to prolonged “net negative emission” carbon dioxide removal (CDR) from (a) marine sink enhancement methods such as ocean fertilization or alkalinity enhancement; (b) terrestrial sink enhancement methods such as afforestation/reforestation, biochar, or soil carbon management; (c) enhanced weathering on land; and (d) bioenergy with carbon capture and storage (BECCS). All carbon exchanges depicted in Fig. 1a also occur here. Note that when net emissions are negative, it is still possible to have some fossil fuel emissions, but these are not depicted here. Adapted from [1••, 71•]