Predicting “Unprecedented change”: A crisis for analogs

Earth System Science (ESS) and climate change research largely rely on predictive computer models. Models represent Earth’s processes and aim to provide policy-relevant information. Despite models’ dominance today, there were other ways to envisage the future. This article examines another method that scientists proposed to foresee the effects of anthropogenic climate change: analogs. An analog is a state of the Earth that is compositionally similar to a poorly understood past or future Earth state. The analog method uses the properties of the better-known state to fill in information about the poorly known state. During the late 1980s and the early 2000s, ecologists promoted the analog method as an alternative to the reductionism of models, especially for understanding the effects of human-caused climate change. Ecologists worried that models omitted and oversimplified biological phenomena whereas analogs captured ecological complexity. Yet promoters of the analog technique faced an epistemological crisis with anthropogenic climate change, which scientists increasingly framed as “unprecedented.” This formulation meant that there would be no analogs in the future. Promoters of analogs thus worked to demarcate how analogs could still be relevant to ESS and predictive climate models.