Pioneers of the ice age models: a brief history from Agassiz to Milankovitch

It is now widely accepted that astronomical factors trigger the emergence of glacial and interglacial periods. However, nearly two centuries ago, the overall situation was not as apparent as it is today. In this article, I briefly discuss the astronomical model of ice ages put forward in the 19th and early 20th centuries. This period was indeed anni mirabiles for scientists to understand the ice age phenomenon. Agassiz, Adhémar and Croll laid the foundation stones for understanding the dynamics of ice ages. But it was Milankovitch who combined empirical geology with mathematical astronomy. Specifically, he identified the shortcomings of the preceding ice age models and modified his model accordingly. In what follows, I review earlier approaches to the ice age problem and show how they failed to meet their objectives. Next, I show how Milankovitch's model managed to capture all sufficient astronomical elements. The final sections focus on Milutin Milankovitch's successful approach, including his accomplishment of tackling the problem mathematically.