The famous mathematician John von Neumann called climate engineering a “thoroughly ‘abnormal’ industry,” arguing that large-scale interventions, including solar radiation management, were not necessarily rational undertakings and could have “rather fantastic effects” on a scale difficult to imagine. Tinkering with the Earth’s heat budget or the atmosphere’s general circulation, he said, “will merge each nation’s affairs with those of every other, more thoroughly than the threat of a nuclear or any other war may already have done”—and possibly leading to “forms of climatic warfare as yet unimagined.”