Synergies and trade-offs in climate action assessments: From stakeholder workshops, systematic literature review, and expert dialogues to a holistic assessment of CDR measures

Abstract

Climate and net-zero GHG emissions targets following the Paris Agreement have increased the pressure for climate actions. A broad range of mitigation measures are necessary for immediate and drastic emissions reductions in all sectors. Furthermore, net-zero and later net-negative GHG emission targets underscore the need for carbon dioxide removal (CDR) measures, since hard-to-abate residual emissions are “very likely” (IPCC, 2022) to remain until the end of the century. Vulnerable communities are already experiencing impacts of climate change now, making adaptation measures increasingly necessary to address existing risks (IPCC, 2023). The implementation of all these measures can however result in significant impacts on humans and the environment. While the knowledge about biogeophysical and biogeochemical impacts on the earth system (e.g., turbulent heat flux, gross CO2 emissions and sinks) is increasing (e.g., Pongratz et al., 2021), integrated and

multidimensional assessments of synergies and trade-offs are scarce (e.g., Singh et al. 2020).

The BMBF funding lines CDRterra and CDRmare address this gap by evaluating synergies and trade-offs of land- and ocean-based CDR measures in a holistic and interdisciplinary approach. Therefore, the research projects CDRSynTra, STEPSEC, and ASMASYS, among others, develop and apply multi-criteria evaluation frameworks, allowing for the integration of biogeophysical and biogeochemical modelling results as well as technological, socio-economic, and political context conditions. This is the first time that a special focus will be placed on ethical considerations as well as social perception. A large set of indicators will be collected, discussed, and weighted through literature research, expert judgment, and participatory stakeholder engagement.

The objectives of this presentation are twofold. First, based on a systematic literature review, the consideration of synergies and trade-offs in prevailing climate action assessments is highlighted. This includes, among other things, the identification of dimensions and indicators used to capture synergies and trade-offs. Differences in existing approaches are explicitly highlighted. Additionally, existing limitations and challenges of these assessments, such as temporal considerations and context conditions, are outlined. The findings will be complemented by the results of two stakeholder workshops. In a second step, we will present the current development of an assessment framework from CDRterra and CDRmare. This framework consists of (i) future sustainable, low-risk scenarios (i.e., several different CDR portfolios embedded in two specific climate targets) which will be assessed by (ii) a comparative multi-dimensional evaluation matrix. We will discuss our development process (stakeholder engagement, scientific workshops, expert dialogue), the assumptions we made, and further explain dimensions, criteria, and indicators of the evaluation matrix.