Earth's last ice age ended around 11,700 years ago and a new study predicts the next one should be 10,000 years away.
But the researchers say record rates of fossil fuel burning that are increasing global temperatures will likely delay this due date.
The findings, published in the journal Science, found fluctuations in Earth's orbit caused Northern Hemisphere ice sheets to expand and retract in natural cycles every 100,000 years.
"We found a predictable pattern over the past million years for the timing of when Earth's climate changes between glacial 'ice ages' and mild warm periods like today, called interglacials," Lorraine Lisiecki, a paleoceanographer at the University of California, Santa Barbara, US, told reporters.
Earth's 'eccentric' orbit of the sun determines ice ages.
Researchers have long suspected changes in the Earth's orbit of the sun are involved in determining when ice ages occur.
Lisiecki's group took a new approach to the problem by looking at the climate record over the last 900,000 years.
They mapped changes in ice sheet volumes using data from fossilized deep-sea organisms, then compared this data to the Earth's oval-shaped orbit around the sun, a phenomenon called orbital eccentricity.
The authors found each glaciation period in the last 900,000 years followed a predictable pattern.
Transitions between glacial and interglacial periods matched up with small variations in the shape of the Earth's orbit of the sun — how the Earth ‘wobbles' in space — and the angle of the planet's tilt axis.
Previous studies have argued the timing of ice ages is random. This study's authors say ice ages follow set rules.
This means it's possible to predict when ice ages will occur based on changes to the Earth's orbit. The next one, they say, will be within the next 11,000 years.
Could CO2 emissions delay the next ice age?
What remains unclear is how human-made climate change would alter these predictions, which are based on pre-industrial Earth conditions.
Some research suggests the CO2 released from burning fossil fuels could cause the planet to repeatedly skip glacial periods for at least the next 500,000 years.
"Such a transition to a glacial state in 10,000 years' time is very unlikely to happen because human emissions of carbon dioxide into the atmosphere have already diverted the climate from its natural course, with longer-term impacts into the future," said co-author Gregor Knorr, a palaeoclimatologist at the Alfred Wegener Institute, Germany.
The researchers say their new model is the first step in understanding how humans affect long-term climate shifts by observing patterns free from industrial activity.
It means future work that includes data from the post-industrial period will likely push back the timing of the next ice age.
