Solomon Hsiang is representative of a new generation in the geosciences community, whose work spans several disciplines, drawing on methods and concepts from far outside the traditional physical science domain in order to make progress on difficult questions at the intersection of natural science, social science, and public policy. Broadly speaking, by examining how humanity has responded to climate variability and change in the distant and recent past, Sol’s research elucidates the question of how humanity may respond to a changing climate in the future. Combining large, independent sets of social science, meteorological, and climatological data and analyzing them with tools more common in microeconomics than natural science, Sol, still at an early stage of his career, has made critical contributions to an incipient revolution in our understanding of the sensitivity and adaptability of humans and their social arrangements to climate variability and change. Such insights will greatly improve the information base from which effective public policy is developed.
A key focus of Sol’s work has been the relation between violent conflict and climate variability and change. Although a considerable amount of research had speculated on such a connection and argued the case in specific instances, Sol’s research demonstrates a pervasive influence of climate variability and change across a very large range of time and spatial scales. In “Civil Conflicts Are Associated With Global Climate,” Sol and coworkers Mark Cane and Kyle Meng demonstrate that new civil conflict in the tropics doubles during El Niño years relative to La Niña years. This paper was the first to show a relationship between social stability and global features of the climate system. The paper is both notable in its findings and characteristic of Sol’s work in its careful analysis of geophysical data (El Niño–Southern Oscillation indicators and surface temperatures) in order to establish a cleverly designed natural experiment of the sort typical in the social sciences. In this case, societal responses as measured by standard indicators of violence were compared not only across El Niño and La Niña periods but also for strongly versus weakly teleconnected regions in order to ferret out a robust signal.
This work was complemented recently by “Quantifying the Influence of Climate on Human Conflict” with collaborators Marshall Burke and Edward Miguel. This meta-analysis of dozens of studies linking weather or climate with conflict provides a compelling picture of social phenomena playing out across a very large range of spatial and temporal scales, ranging from episodes of interpersonal violence to decade-scale wars and multicentury-scale catastrophic societal collapse, with a common driving force.
Sol’s work continues to break new ground as he explores other arenas where climate generates economically and socially important responses by people that cause further socioeconomic ripple effects, including changes in labor productivity, agricultural land use, and income and family structure following tropical cyclone strikes. Taken together, these and related research findings are reinventing the nature of the knowledge base available to governments and individuals as they make choices for dealing with a rapidly changing climate.
—MICHAEL OPPENHEIMER, Princeton University, Princeton, N. J.