According to a new study, changes in Earth’s tilt have driven the rise and fall of massive ice sheets for the past 800,000 years, shaping the planet’s climate and triggering at least eight ice ages.
The research, published Thursday, February 27, in the journal Science, found a strong connection between Earth’s axial tilt and the formation of ice sheets. Based on these patterns, scientists estimate that another ice age would likely begin in about 11,000 years. However, human-caused global warming may prevent it.
Ice ages occur roughly every 100,000 years
Ice ages, which occur roughly every 100,000 years, are periods when thick ice sheets expand across large parts of the planet, lasting thousands of years. These glacial periods are followed by warmer interglacial phases when the ice retreats. Earth is in an interglacial period, with the last ice age peaking around 20,000 years ago.
For over a century, scientists have studied how Earth’s position and tilt affect the growth of ice sheets. Serbian scientist Milutin Milankovitch proposed in the 1920s that small shifts in Earth’s axial tilt and orbit shape could trigger massive glaciations.
Next ice age would hit Earth in 11,000 years if it weren't for climate change, scientists say | Sascha Pare, LiveScience
Scientists have determined exactly how Earth's orbit and tilt affect glaciation and deglaciation, based on the length of these parameters' cycles and clues… pic.twitter.com/g8g2QAQ2fu
— Owen Gregorian (@OwenGregorian) February 28, 2025
A 1976 study provided geological evidence supporting this idea, showing that two key factors—Earth’s tilt and the way its axis wobbles—affect ice sheet cycles. However, the exact role of each remained unclear.
Researchers now believe they have untangled how these factors influence ice sheet behavior.
Shifts in Earth’s tilt and wobble
Earth’s axis is tilted at a 23.5-degree angle, affecting how much sunlight reaches different parts of the planet. This tilt naturally changes in a cycle lasting about 41,000 years. At the same time, the planet’s axis wobbles like a spinning top, altering sunlight exposure in a separate cycle of about 21,000 years.
Scientists mapped shifts in Earth’s tilt and wobble over the past 800,000 years to understand these influences better. They compared this data with ice sheet growth and retreat records using tiny fossil shells in ocean sediment. These shells contain oxygen levels that reveal how far ice sheets extended when the organisms were alive, said lead author Stephen Barker, a professor at Cardiff University in the U.K.
The results were striking, Barker said, calling it a “fall off the chair moment.” The study found that changes in Earth’s tilt control ice sheet expansion from the poles toward the equator. In contrast, the planet’s wobble influences ice sheet retreat toward the poles more.
If Earth were following its natural cycles, another ice age would likely begin in about 10,000 years. However, researchers warn that human-driven greenhouse gas emissions are changing the planet’s climate so much that future ice ages may not occur.
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