As the international community’s best expression of a collective vision of a desirable future, the 2015 UN Sustainable Development Goals (SDGs) present a framework against which to assess the broader impact of emerging technologies. Implications of technologies and practices for removing CO₂ from the atmosphere (CDR) are not fully understood and have not yet been mapped against the full range of SDGs. CDR is widely seen as necessary to achieve the Paris Agreement’s global goal of limiting warming to 1.5-2°C, yet local geographical, socio-economic, and political interdependencies are often overlooked. This review synthesizes the best available understandings of potential implications of CDR options aiming to complement emissions reductions. It seeks to identify effects on and interactions between specific social, environmental, and policy environments, in which various CDR options could be pursued. Climate change mitigation and co-benefits from CDR could significantly benefit SDGs, yet poorly designed CDR policies could also challenge SDGs. Specific CDR options could generate conflicts over land, water, biomass, or electric power resources, and exclude communities from policy benefits with negative cascading effects for a range of SDGs. In the literature, implications of CDR activities on sustainable development are derived from current pilot activities, inferred from similar practices already operational or model outputs regarding land, energy, or material requirements. Important gaps remain. We identify questions for further disciplinary and inter- or transdisciplinary work strengthening understanding of how CDR could either support or threaten the achievement of the SDGs. Key policy insights

The Paris Agreement requires mitigation contributions from all Parties. Therefore, the determination of additionality of activities under the market mechanisms of its Article 6 will need to be revisited. This paper provides recommendations on how to operationalize additionality under Article 6. We first review generic definitions of additionality and current approaches for testing of additionality before discussing under which conditions additionality testing of specific activities or policies is still necessary under the new context of the Paris Agreement, that is, in order to prevent increases of global emissions. We argue that the possibility of ‘hot air’ generation under nationally-determined contributions (NDCs) requires an independent check of the NDC’s ambition. If the NDC of the transferring country does contain ‘hot air’, or if the transferred emission reductions are not covered by the NDC, a dedicated additionality test should be required. While additionality tests of projects and programmes could continue to be done through investment analysis, for policy instruments new approaches are required. They should be differentiated according to type of policy instrument. For regulation, we suggest calculating the resulting pay-back period for technology users. If the regulation generates investments exceeding a payback period threshold, it could be deemed additional. Similarly, carbon pricing policies that generate a carbon price exceeding a threshold could qualify; for trading schemes an absence of over-allocation needs to be shown. The threshold should be differentiated according to country categories and rise over time. Key policy insights