Fig. 1: Annual global temperatures from 1850 to 2017 shown in warming stripes. The color scale represents the change in global temperatures covering 1.35°C. Source: https://www.climate-lab-book.ac.uk/2018/warming-stripes/And, do we rely too much on so-called ‘silver bullet’-solutions in the known scenarios? These are two of the central questions of a recent publication by Waszawski et al. published in Environmental Research Letters. Among the coauthors are Earth League Fellows Tim Lenton, Daniela Jacob, Nebojsa Nakicenovic, Hans Joachim Schellnhuber, and Kazuhiko Takeuchi, as well as Earth League co-chairs Peter Schlosser and Johan Rockström. The study that is based on the results of the 2019 Annual Earth League Workshop (“Towards a 1.5 °C world: Challenges and Solutions”) investigated 50 of the SR1.5 scenarios (the currently known scenarios with which global warming can be limited to 1.5°C with low or no overshoot) of the IPCC with regard to their feasibility and limits. Available technologies and other options to reduce CO2 (‘levers’) were investigated for their feasibility by determining within which boundaries they could be used at a ‘reasonable’ (most desirable), ‘challenging’ or ‘speculative’ level when they would be deployed at such a large scale as implied by the scenarios. None of the scenarios were able to limit global warming to 1.5 °C as stated in the Paris Agreement when all levers were only used within ‘reasonable’ boundaries. When at least one of the five levers was allowed to be used within ‘challenging’ boundaries, less than half of the scenarios were able to limit global warming. Additionally, most of the scenarios used geological CO2 storage methods beyond what is currently acknowledged to be feasible (‘silver bullet’-solution).
The analysis of the study clearly showed that global warming can only be limited when we do not rely on ‘silver bullet’-solutions such as geological CO2 storage but also consider using all available levers, such as changes in the energy sector, land use, or changing diets. The world is at high risk of exceeding the 1.5 °C target. Moreover, the window of opportunity for action to meet the climate targets from the Paris Agreement is closing fast. In order to meet this target, we need deep societal and economic transformations in agreement with the UN Sustainable Development Goals.
Lila Warszawski, Elmar Kriegler, Timothy M. Lenton, Owen Gaffney, Daniela Jacob, Daniel Klingenfeld, Ryu Koide, María Máñez Costa, Dirk Messner, Nebojsa Nakicenovic, Hans Joachim Schellnhuber, Peter Schlosser, Kazuhiko Takeuchi, Sander van der Leeuw, Gail Whiteman, Johan Rockström (2021): All options, not silver bullets, needed to limit global warming to 1.5°C: a scenario appraisal. Environmental Research Letters [DOI:10.1088/1748-9326/abfeec]
