Summary/Abstract
This contribution explores the role of quantified scientific expertise for U.S. geoengineering politics. Drawing on empirical evidence from federal proceedings, it assesses how climate measures, models, targets, and thresholds have shaped the trajectory of geoengineering within U.S. climate policy between 1990 and 2015. The analysis distinguishes three stages, in which this “career” of geoengineering has been advanced, each pointing to distinct capacities of quantified expertise: from contesting the “discernible human influence” on the climate, to quantifying the size of this challenge, all the way to devising an “emergency tool”. Going beyond the specific case of geoengineering, this contribution thus illuminates how context dependent not only our understanding of societal problems is, but also our comprehension of the kinds of responses we deem legitimate. Specifically, it demonstrates how numbers “work” in communicating global challenges, and how they guide the choices we make in seeking to address them.