The debate over climate change in historical time, i.e. the period in human history for which written record exists, goes back to the quarrel between the Ancients and the Moderns which involved a “dispute of the New World” (Antonella Gerbi). In this context, naturalists of the eighteenth century discussed whether the climate of the Italian peninsula had been warmer and more humid in Antiquity as compared with the present, whether there had occurred a deterioration of climatic conditions that contributed to the decline of the Roman Empire (Edward Gibbon) and, last but not least, how the climates of North America compared to European climates (Buffon, Jefferson etc.). How did climatic differences between the Old and the New World relate to differences in flora and fauna, and what did it mean for Europeans to migrate and adapt to climates in North America? Last but not least, European colonizers around the world sought to modify weather conditions, particularly in tropical colonies, through measures such as deforestation and desiccation. In principle, these debates are well known; however, neither has their scope been fully explored, nor has their relevance for the emergence of climatology as a scientific discipline been recognized. This maybe so because leading innovators in the field of climatology – e.g. Humboldt, Arago and Schouw – remained skeptical about the evidence or even rejected the idea of climate change entirely; or maybe because the nineteenth century made the groundbreaking discovery of geologic time and the Ice Ages. The Ice Ages of the Pleistocene made the Holocene climate look so stable that only very few climatologists attributed any significance to the variability of the latter. It took until the 1950s, before the idea of climate change in historical time experienced a revival that led to the foundation of a new branch, historical climatology (Lamb, Le Roy Ladurie, Pfister). This paper will review the debate on climate change in historical time between 1700 and 1850 and place it in the context of the “climatological revolution,” a term I am using to denote the emergence of climatology as a scientific discipline around 1800.