How bad is it if adaptation decisions are influenced by typical climate attribution results? On the link between time of emergence and the crossing of adaptation-relevant hazard thresholds

Most common climate-scientific attribution studies check for, or quantify, the influence of combined anthropogenic climate forcing to date on an observed change or event. Besides fulfilling a range of well-evidenced roles in society, attribution findings are also commonly quoted together with calls specifically for, or even financial prioritisation of, climate change adaptation to the respective climate hazard in the respective region. Notions of adaptation deservedness as well as differentiated availability and applicability of scientific data and tools and other practical issues contraindicate this conclusion. More fundamentally, it also hinges on the degree to which the emergence of an anthropogenic change signal in observations to date is indicative of future climate hazards relevant to adaptation.

Here, we address this question by analysing the link between selected hazards’, or climatic-impact drivers’, Time of Emergence on the one hand, and the exceedence of adaptation-relevant relative and absolute thresholds on the other hand, at subcontinental scales globally. Time of emergence is defined following common standards in the recent literature; climatic-impact drivers (heat and cold, wet and dry) are chosen based on the latest IPCC report; thresholds relevant for adaptation in different impact sectors are refined based on expert judgment in interdisciplinary cooperation. The analysis is performed on large-ensemble climate model data from CMIP6’s Detection and Attribution (DAMIP) and Scenario Model (ScenarioMIP) Intercomparison Projects and observational climate data consulted for reference.

Our results show the globally differentiated error that is made when drawing a direct link between a typical climate-scientific attribution results and adaptation-relevant climate change. Factors contributing to this complexity include changes in anthropogenic non-greenhouse gas climate forcings, spatially differing internal climate variability, and present-day climatology, for example. We acknowledge methodological caveats, draw further implications for climate justice and global adaptation, and discuss the potential of additional climate projection-based evidence for effective communication.