The ‘Winter’ Analogy Fallacy

From superbombs to supervolcanoes


  • Matthias Dörries Université Louis Pasteur


In the late 1980s, a few volcanologists created an ill-founded analogy. Drawing upon the then-fashionable ‘nuclear winter’ theory, they claimed that certain explosive eruptions in historic times might have led to ‘volcanic winters.’ The nuclear winter debate of the 1980s was about the possibly disastrous effects of a nuclear war on the Earth's atmosphere and climate, thus on agriculture, and human beings; the term implied that the dust and soot released into the atmosphere by nuclear bombs and the resulting fires would drop world-wide temperatures enough to turn summer into winter. Major effects, it was inferred then, would last for weeks or at most a few months. The exact consequences of nuclear war remained subject to a lively debate lasting throughout the 1980s. Modeling was still in its infancy, and uncertainty was high. This was also true of research into the topic of volcanism and climate. The global influence of explosive volcanic eruptions on the Earth’s climate was still contested by volcanologists, who in the early 1980s had grudgingly conceded to atmospheric scientists’ argument that it was not volcanic dust, but sulphate aerosols in the stratosphere that affected global atmospheric temperatures (and this, as increasingly became clear, for periods of more than three years). Given the uncertainties in both models and the significant differences concerning the causes (dust and soot, versus sulphates) and length (three months to several years), the analogy between ‘nuclear winter’ and ‘ volcanic winter’ was unsubstantiated, having only a vague commonality in a shortterm diminution of global temperatures. In fact, as I will show, the analogy never underwent scrutiny, debate or substantiation, as some volcanologists succeeded in turning a passing speculation into a matter of fact.