Final answer:
Changes in Earth's rotational axis tilt and orbital variations, particularly the Milankovich cycles, are key contributors to the glacial cycles experienced over the past million years.
Step-by-step explanation:
The combination of changes in Earth's rotational axis tilt and orbital variations are responsible for the glacial cycles of the last million years.
Through his work, Serbian astronomer Milutin Milankovich linked glacial cycles to the precession of Earth's orbit. He suggested that colder winters led to more snow, which fed the glaciers and caused the ice ages. As snow reflects sunlight, the white-covered land warms up less effectively after winter, leading to a balance disruption in the climate.
Furthermore, natural drivers of climate change such as Milankovich cycles, changes in solar activity, and volcanic eruptions contribute to these cycles. During periods like the Medieval Climate Anomaly and the Little Ice Age, significant climate shift patterns have been identified, suggesting the powerful impact of these combined natural factors.