How did deserts become more widespread during the Cenozoic Era?

Deserts as we recognize them today are geologically recent, having emerged as a result of the progressive cooling and subsequent aridification of global climates throughout the Cenozoic Era.1

This widespread aridification was driven by several key factors:

• Tectonic Shifts: Significant tectonic movements altered the positions of continents and ocean passages, fundamentally changing global atmospheric and oceanic circulation. For instance, the opening of the Drake Passage isolated Antarctica, contributing to a long-term global cooling trend.2
• Atmospheric Changes: Decreasing concentrations of carbon dioxide during the Cenozoic are believed to have initiated and sustained this cooling, which fostered the development of arid environments.2
• Mountain Building: The uplift of major mountain ranges, such as the Andes and the Tibetan Plateau, created rain shadows that sheltered interior regions from precipitation, further promoting desert formation.21

As these global conditions shifted, desert surfaces expanded at the expense of adjacent forested zones, a process that continued through the Pleistocene and Holocene epochs.3