For nearly a million years, the Earth’s climate has shifted between freezing ice ages and warmer periods. A new study finds that these changes are closely linked to the planet’s tilt.
Given this finding, scientists predict that under natural conditions, another ice age would begin in about 11,000 years. However, rising global temperatures caused by human activity may disrupt this cycle.
Ice ages follow a predictable pattern
Ice ages occur roughly every 100,000 years. During these times, massive ice sheets expand over large areas, lasting for thousands of years. Warmer interglacial periods follow, causing the ice to shrink. The Earth is currently in one of these warmer phases, with the last ice age having reached its peak about 20,000 years ago.
Scientists have long studied how the Earth’s position in space affects these climate shifts. In the 1920s, Serbian scientist Milutin Milankovitch suggested that small changes in the Earth’s orbit and tilt could trigger major glaciations.
A 1976 study confirmed that two key factors – the Earth’s tilt and the way its axis wobbles – play a role in ice sheet cycles. However, researchers were unsure which factor had the strongest influence.
Earth’s tilt controls ice growth
The Earth tilts at a 23.5-degree angle, which affects how much sunlight different parts of the planet receive. This tilt changes slightly over the course of a cycle that lasts about 41,000 years. At the same time, the Earth’s axis wobbles like a spinning top, altering sunlight exposure every 21,000 years.
Next ice age would hit Earth in 11,000 years if it weren't for climate change, scientists say | Sascha Pare, LiveScience
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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
To understand these effects, scientists analyzed the Earth’s tilt and wobble over the past 800,000 years. They compared this data with ocean sediment records, which contain tiny fossil shells. According to Stephen Barker, a professor at Cardiff University and the lead author of the study, these fossils hold oxygen levels that indicate the size of ice sheets when they were formed.
The findings revealed a clear pattern. Ice sheets grow when the Earth’s tilt decreases, limiting sunlight in colder regions. In contrast, the planet’s wobble plays a larger role in causing ice sheets to shrink.
Given these findings, scientists believe that under natural conditions, another ice age would likely begin in about 10,000 to 11,000 years. However, human-driven climate change may prevent it. Scientists warn that greenhouse gas emissions are warming the planet at an unprecedented rate, which could disrupt the natural ice age cycle.
While past ice ages followed a predictable pattern, today’s climate is changing in new ways. Researchers say more studies are needed to understand how human activity will impact long-term climate shifts. If greenhouse gas emissions continue, the Earth’s natural cooling and warming cycles may never return to their original rhythm.