Contextualizing Climate Engineering and Mitigation: Illusion, Complement, or Substitute? (CEMICS)

• Applicants: Professor Dr. Ottmar Edenhofer; Professor Jens Hartmann, Ph.D.; Professor Dr. Hermann Held; Professor Dr. Elmar Kriegler; Dr. Stefan Schäfer, since 2/2017; Professor Dr. Harald Stelzer
• Subject Area: Economic Policy, Applied Economics ; Mineralogy, Petrology and Geochemistry ; Palaeontology ; Atmospheric Science ; Practical Philosophy ; Economic Theory
• Term: from 2013 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 236842296

• Final Report Year: 2021

Final Report Abstract

CEMICS was driven by the hypothesis that society will not take decisions on climate engineering (CE) in isolation. CEMICS1 put CE in the context of mitigation. We investigated the climate effects, costs, benefits, and side-effects of afforestation/reforestation (AF), enhanced weathering of rocks (EW), direct air capture (DAC) and stratospheric aerosol injection (SAI). CEMICS2 expanded the analysis of carbon dioxide removal (CDR) to include significant synergies and trade-offs between different CDR options and analysed the dependency of CE deployment in the context of options and targets, ethical approaches and arguments, and societal developments and goals. CEMICS focussed also on a co-deployment of CDR options like EW and Biochar with AF and bioenergy plants for sustainable CO2 storage in biomass. Under some conditions the combined application of CDR options would result in beneficial effects like higher food production, healthier soils or forests and less acidic ocean water. Future scenarios of large-scale biomass-based CDR deployment neglecting nutrient deficiencies overestimate the CO2 removal potential, and the co-deployment of EW could counteract this limitation. Assessment of large scale afforestation and reforestation suggests negative effects on food prices, which can be mitigated by limiting afforestation to the tropics. The CDR-technologies AF, EW, and DACCS were integrated into REMIND-MAgPIE allowing to assess the value of single CDR options for climate change mitigation as well as the associated impacts and risks. Achieving the 1.5°C target requires considerable amounts of CDR whereas 2°C would still be feasible without CDR, but only if emissions are halved every decade. Surprisingly, the CDR demand is almost independent of the socio-economic development (SSP). To avoid the resulting high mitigation costs and their distributional consequences, some amount of CDR will be necessary also for the 2°C target. Regional CDR deployment patterns depend on the option. Therefore, different CDR options should be developed such that all regions can contribute according to their regional potentials. In addition to CDR, the first target-based integrated analyses of SAI and mitigation recognized not only global mean temperature change, but also side effects like regional climate pattern mismatch or stratospheric ozone depletion. This target-based approach, beyond a global mean temperature focus, ensured consistent usage of ethical assumptions, and led to a qualitative reduction of SAI in the combined SAI-mitigation options portfolio. Surprisingly, in the review process, the twin conceptual innovation ‘extension of the ethics of the global temperature target to SAI and its integration in cost risk analysis’ was perceived as more fundamental than anticipated. For the ethical analysis much depends on the normative framework, especially the values under considerations and their weighing in case of value-conflicts. CEMICS created risk profiles for different technologies as well as normatively informed guardrails allowing for a comparison and answering questions of moral permissibility of distinct options. A normative framework for the evaluation of CE options, based on possible consequences, the distribution of associated risks, feasibility constraints and sustainability criteria, was developed. Finally, this framework was linked to SDGs as well as RCPs and SSPs. Media interest in our work resulted in seven radio and four TV-interviews, contribution to 17 news articles and three cases of scientific advisory service.

Publications

• 2014. Land-use protection for climate change mitigation Nature Clim. Change 41095–8
  Popp A, Humpenöder F, Weindl I, Bodirsky B L, Bonsch M, Lotze-Campen H, Müller C, Biewald A, Rolinski S, Stevanovic M and Dietrich J P
  
• 2016. Afforestation to mitigate climate change: impacts on food prices under consideration of albedo effects. Environ. Res. Lett. 11, 085001
  Kreidenweis, U., Humpenöder, F., Stevanović, M., Bodirsky, B.L., Kriegler, E., Lotze-Campen, H., Popp, A.
  
• 2017. Towards a comprehensive climate impacts assessment of solar geoengineering. Earths Future 5, 93–106
  Irvine, P.J., Kravitz, B., Lawrence, M.G., Gerten, D., Caminade, C., Gosling, S.N., Hendy, E.J., Kassie, B.T., Kissling, W.D., Muri, H., Oschlies, A., Smith, S.J.
  
• 2018. Potential and costs of carbon dioxide removal by enhanced weathering of rocks. Environ. Res. Lett. 13, 034010
  Strefler, J., Amann, T., Bauer, N., Kriegler, E., Hartmann, J.
  
• 2019. Cost-Risk Trade-Off of Mitigation and Solar Geoengineering: Considering Regional Disparities Under Probabilistic Climate Sensitivity. Environ. Resour. Econ. 72, 263–279
  Roshan, E., M. Khabbazan, M., Held, H.
  
• 2019. Ideas and perspectives: Synergies from co-deployment of negative emission technologies. Biogeosciences 16, 2949–2960
  Amann, T., Hartmann, J.
  
• 2020. Impacts of enhanced weathering on biomass production for negative emission technologies and soil hydrology. Biogeosciences 17, 2107–2133
  de Oliveira Garcia, W., Amann, T., Hartmann, J., Karstens, K., Popp, A., Boysen, L.R., Smith, P., Goll, D.
  
• 2020. Responsible Innovation and Climate Engineering. A Step Back to Technology Assessment. Philos. Manag. 19, 19:297–316
  Stelzer, H.
  
• 2021. Alternative carbon price trajectories can avoid excessive carbon removal. Nature Communications 12, 2264
  Strefler, J., Kriegler, E., Bauer, N., Luderer, G., Pietzcker, R.C., Gianniusakis, A., Edenhofer, O.