Only few realistic scenarios remain to limit global warming to 1.5°C

Daniela Jacob und María Máñez Costa co-authors of new study on the 1.5°C target

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In the IPCC Special Report on 1.5°C Global Warming, more than 400 climate scenarios were evaluated. However, only 50 of these scenarios will limit global warming to 1.5°C and only 20 of them make realistic assumptions about mitigation options, such as the amount of reforestation or the amount of CO₂ extraction from the atmosphere.

The study “All options, not silver bullets, needed to limit global warming to 1.5°C: a scenario appraisal“ that is based on discussions from the annual Earth League Workshop, which took place at the Climate Service Center Germany (GERICS) in 2019, covers two central questions:

1. How realistic are the 50 IPCC scenarios and pathways?
2. Do the scenarios use all available technologies and options to reduce CO₂ emissions? Or do they rely too much on so-called „silver bullet“-solutions?

The analysis indicates that in the 20 scenarios with realistic assumptions, at least one of five available mitigation levers would have to be moved to a rather "challenging" extent to meet the 1.5°C target. Therefore, the world is at high risk of exceeding this limit. Moreover, the window of opportunity for action to meet the climate targets from the Paris Agreement is closing fast (question 1).

Additionally, many of the scenarios rely too much on geological carbon storage methods beyond their current feasibility („silver bullet“ solution). In order to meet the 1.5°C target, it is necessary to use all available levers, such as the energy sector, land use or changing diets. "None of the realistic scenarios relies on a single silver bullet," says lead author Lila Warszawski of the Potsdam Institute for Climate Impact Research (PIK).

Less than half of the IPCC scenarios that enable us to meet the 1.5°C target rely on realistic assumptions. All available technologies and options need to be exhausted instead of build on single „silver bullet“ solutions only. Meeting the 1.5°C target as formulated in the Paris Agreement will only be possible by deep societal and economic transformations in agreement with the UN Sustainable Development Goals.

The Study

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]