Editing IPCC:AR6/WGIII/Chapter-14 (section)

==== 14.4.5.1 Global Governance of Solar Radiation Modification and Associated Risks ====

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Solar radiation modification, in the literature also referred to as ‘solar geoengineering’, refers to the intentional modification of the Earth’s shortwave radiative budget, such as by increasing the reflection of sunlight back to space, with the aim of reducing warming. Several SRM options have been proposed, including stratospheric aerosol injection (SAI), marine cloud brightening (MCB), ground-based albedo modifications (GBAM), and ocean albedo change (OAC). SRM has been discussed as a potential response option within a broader climate risk management strategy, as a supplement to emissions reduction, carbon dioxide removal and adaptation ( [[#Crutzen--2006|Crutzen 2006]] ; [[#Shepherd--2009|Shepherd 2009]] ; [[#Caldeira--2017|Caldeira and Bala 2017]] ; [[#Buck--2020|Buck et al. 2020]] ), for example as a temporary measure to slow the rate of warming ( [[#Keith--2015|Keith and MacMartin 2015]] ) or address temperature overshoot ( [[#MacMartin--2018|MacMartin et al. 2018]] ; [[#Tilmes--2020|Tilmes et al. 2020]] ). SRM assessments of potential benefits and risks still primarily rely on modelling efforts and their underlying scenario assumptions ( [[#Sugiyama--2018a|Sugiyama et al. 2018a]] ), for example in the context of the Geoengineering Model Intercomparison Project GeoMIP6 ( [[#Kravitz--2015|Kravitz et al. 2015]] ). Recently, small-scale MCB and OAC experiments started to take place on the Great Barrier Reef ( [[#McDonald--2019|McDonald et al. 2019]] ).

SAI – the most researched SRM method – poses significant international governance challenges since it could potentially be deployed uni- or minilaterally and alter the global mean temperature much faster than any other climate policy measure, at comparatively low direct costs ( [[#Parson--2014|Parson 2014]] ; [[#Nicholson--2018|Nicholson et al. 2018]] ; [[#Smith--2018|Smith and Wagner 2018]] ; [[#Sugiyama--2018b|Sugiyama et al. 2018b]] ; [[#Reynolds--2019a|Reynolds 2019a]] ). While being dependent on the design of deployment systems, both geophysical benefits and adverse effects would potentially be unevenly distributed (AR6 WGI, Chapter 4). Perceived local harm could exacerbate geopolitical conflicts, not least depending on which countries are part of a deployment coalition ( [[#Maas--2012|Maas and Scheffran 2012]] ; [[#Zürn--2013|Zürn and Schäfer 2013]] ), but also because immediate attribution of climatic impacts to detected SAI deployment would not be possible. Uncoordinated or poorly researched deployment by a limited number of states, triggered by perceived climate emergencies, could create international tensions ( [[#Corry--2017|Corry 2017]] ; [[#Lederer--2018|Lederer and Kreuter 2018]] ). An additional risk is that of rapid temperature rise following an abrupt end of SAI activities ( [[#Parker--2018|Parker and Irvine 2018]] ; [[#Rabitz--2019|Rabitz 2019]] ).

While there is room for national and even sub-national governance of SAI – for example on research (differentiating indoor from open-air) ( [[#Jinnah--2018|Jinnah et al. 2018]] ; [[#Hubert--2020|Hubert 2020]] ) and public engagement ( [[#Bellamy--2017|Bellamy and Lezaun 2017]] ; [[#Flegal--2019|Flegal et al. 2019]] ) – international governance of SAI faces the challenge that comprehensive institutional architectures designed too far in advance could prove either too restrictive or too permissive in light of subsequent political, institutional, geophysical and technological developments ( [[#Sugiyama--2018a|Sugiyama et al. 2018a]] ; [[#Reynolds--2019a|Reynolds 2019a]] ). Views on governance encompass a broad range, from aiming to restrict to wanting to enable research and potentially deployment; in between these poles, other authors stress the operationalisation of the precautionary approach: preventing deployment until specific criteria regarding scientific consensus, impact assessments and governance issues are met ( [[#Tedsen--2013|Tedsen and Homann 2013]] ; [[#Wieding--2020|Wieding et al. 2020]] ). Many scholars suggest that governance arrangements ought to co-evolve with respective SRM technologies ( [[#Parker--2014|Parker 2014]] ), including that it stay at least one step ahead of research, development, demonstration, and – potentially – deployment ( [[#Rayner--2013|Rayner et al. 2013]] ; [[#Parson--2014|Parson 2014]] ). With the modelling community’s increasing focus on showing that, and in what ways, SAI could help to minimise climate change impacts in the Global South, the SRM governance literature has come to include considerations of how SAI could contribute to global equity ( [[#Horton--2016|Horton and Keith 2016]] ; [[#Flegal--2018|Flegal and Gupta 2018]] ; [[#Hourdequin--2018|Hourdequin 2018]] ).

Given that risks and potential benefits of SRM proposals differ substantially and their large-scale deployment is highly speculative, there is a wide array of concrete proposals for near-term anticipatory or adaptive governance. Numerous authors suggest a wide range of governance principles [[#Nicholson--2018|Nicholson et al. (2018)]] encapsulate most of these in suggesting a list of four: (i) Guard against potential risks and harm; (ii) Enable appropriate research and development of scientific knowledge; (iii) Legitimise any future research or policymaking through active and informed public and expert community engagement; (iv) Ensure that SRM is considered only as a part of a broader, mitigation-centred portfolio of responses to climate change. Regarding international institutionalisation, options range from formal integration into existing UN bodies like the UNFCCC ( [[#Nicholson--2018|Nicholson et al. 2018]] ) or the Convention on Biological Diversity (CBD) ( [[#Bodle--2014|Bodle et al. 2014]] ) to the creation of specific, but less formalised global fora ( [[#Parson--2013|Parson and Ernst 2013]] ) to forms of club governance ( [[#Bodansky--2013|Bodansky 2013]] ; [[#Lloyd--2014|Lloyd and Oppenheimer 2014]] ). Recent years have also seen the emergence of transnational non-state actors focusing on SRM governance, primarily expert networks and NGOs ( [[#Horton--2020|Horton and Koremenos 2020]] ).

Currently, there is no targeted international law relating to SRM, although some multilateral agreements – such as the Convention on Biological Diversity, the UN Convention on the Law of the Sea, the Environmental Modification Convention, and the Vienna Convention on the Protection of the Ozone Layer and its Montreal Protocol – contain provisions applicable to SRM ( [[#Bodansky--2013|Bodansky 2013]] ; [[#Jinnah--2019|Jinnah and Nicholson 2019]] ; [[#Reynolds--2019a|Reynolds 2019a]] ).

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