Earth’s massive ice age cycles, which happen every 100,000 years, might be caused by simple orbital wobbles rather than a mysterious 'internal engine.'
April 17, 2026
Original Paper
A First Principles Approach to the 100,000-year Problem
arXiv · 2604.12143
The Takeaway
For decades, the '100,000-year problem' has been a giant hole in climate science: why do ice ages happen on that specific schedule? Most scientists assumed there was some incredibly complex, 'non-linear' chemical process inside the Earth driving it like a ticking clock. This paper shows that you can explain the whole thing with a simple model involving Earth's orbit and how the ocean stores heat. It strips away the complexity and shows the planet’s climate is far more sensitive to the 'tug' of other planets than we thought. This means our long-term climate history is much more predictable—and potentially more fragile—than we ever realized.
From the abstract
The 100,000-year problem concerns the dominant period of glacial-interglacial cycles over the past 800,000 years and their correlation with Earth's orbital eccentricity, despite eccentricity's weak influence on solar radiation. Two theories compete: the astronomical theory, in which orbital forcing drives the cycles with amplification from Earth system feedbacks, and the geochemical theory, in which internal dynamics dominate with orbital forcing synchronising oscillations. We investigate these