Editing IPCC:AR6/WGI/Chapter-5 (section)

=== 5.6.1 Introduction ===

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Carbon dioxide removal (CDR) refers to anthropogenic activities that seek to remove CO <sub>2</sub> from the atmosphere and durably store it in geological, terrestrial or ocean reservoirs, or in products (Glossary). CO <sub>2</sub> is removed from the atmosphere by enhancing biological or geochemical carbon sinks or by direct capture of CO <sub>2</sub> from air and storage. Solar radiation modification (SRM) refers to the intentional, planetary-scale modification of the Earth’s radiative budget with the aim of limiting global warming. Most proposed SRM methods involve reducing the amount of incoming solar radiation reaching the surface, but others also act on the longwave radiation budget by reducing optical thickness and cloud lifetime (Glossary). SRM does not fall within the IPCC definitions of mitigation and adaptation (Glossary). CDR and SRM are referred to as ‘geoengineering’ in some of the literature, and are considered separately in this report.

This section assesses the implications of CDR and SRM for biogeochemical cycles. CDR has received growing interest as an important mitigation option in emissions scenarios consistent with meeting the Paris Agreement climate goals (SR1.5, SRCCL). The climate effects of CDR and SRM are assessed in Chapter 4, and a detailed assessment of the socio-economic dimensions of these options is presented in AR6 WGIII, Chapters 7 and 12.

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