False Hopes, Missed Opportunities: How Economic Models Affect the IPCC Proposals in Special Report 15 “Global Warming of 1.5 °C” (2018). An Analysis From the Scientific Advisory Board of BUND

The 2018 IPCC Special Report SR15 developed four scenarios how temperature increases could either be limited to 1.5°, or, in the case of overshoot, could be brought back to that level by 2100. However, the Carbon Dioxide Removal options discussed to achieve “negative emissions” will affect not only the climate system, but also biodiversity and the ecosystem services it provides. Unfortunately, the Integrated Assessment Models, and in particular the economic models incorporated in them were capable of integrating only a selective fraction of these effects, and ignore potential tipping points triggering irreversible processes, policies beyond economic instruments and consumption changes to happen over the next 80 years. Our analysis is based on an interdisciplinary expert elicitation, analysing the options suggested by the IPCC one by one. We find that most of them are associated with biodiversity loss, hazardous chemicals dispersion, enhanced energy consumption and/or other severe other damages. We suggest which measures can be applied sustainably, which should be dropped, and which additional ones have been omitted by the report