The question of whether another ice age is coming requires distinguishing between the common use of the term and its scientific definition. Earth is technically in an “Ice Age” right now, a geological period characterized by the presence of permanent ice sheets at the poles. The real question most people are asking is when the next major advance of continental glaciers, known as a glacial period, will begin. The natural timing of these shifts is governed by predictable astronomical forces that alter the distribution of solar energy reaching our planet.
Understanding Glacial and Interglacial Periods
An “Ice Age,” or more formally, a glacial epoch, is any long interval of time when global temperatures are low enough for large ice sheets to exist on the continents. The planet has been in the Late Cenozoic Ice Age for millions of years, cycling between two distinct states.
A glacial period is a colder phase when vast sheets of ice expand from the poles, covering large parts of the continents. During these periods, sea levels drop dramatically because water is locked up in the expanding continental ice. Conversely, an interglacial period is a warmer interval marked by the retreat of these massive ice sheets to the polar regions, which is the state we are in now. Our current interglacial period, the Holocene, began about 11,700 years ago, following the end of the last major glacial advance.
The Astronomical Forces That Drive Ice Ages
The primary natural mechanism driving the cycles of glacial and interglacial periods is known as the Milankovitch Cycles. These cycles describe the collective, long-term effects of changes in Earth’s orbit and rotation on the distribution of solar energy received. While the total energy from the Sun does not change significantly, its distribution across the planet’s surface is altered over tens of thousands of years.
The cycles consist of three components. Eccentricity describes the change in the shape of Earth’s orbit, shifting from nearly circular to more elliptical over a cycle of roughly 100,000 years. Obliquity is the tilt of Earth’s axis, varying between 22.1 and 24.5 degrees on a cycle of about 41,000 years; a smaller tilt promotes ice sheet growth by reducing seasonal contrast.
The third component is precession, the wobble of Earth’s axis, completing a cycle in approximately 21,000 to 26,000 years. The combination of these three cycles determines insolation, or the amount of solar radiation, particularly during the summer in the Northern Hemisphere at high latitudes (around 65° N). Ice sheets primarily grow when Northern Hemisphere summers are too cool to melt the previous winter’s snow, making this regional summer insolation the trigger for a new glacial period.
Predicting the Next Natural Glacial Period
Based purely on the predictable astronomical forces of the Milankovitch Cycles, scientists can calculate the natural trajectory of Earth’s climate. The current combination of orbital parameters suggests Earth is on a natural, slow cooling trend, but the conditions necessary to trigger the extensive growth of continental ice sheets are not imminent.
Specific orbital models tracking past climate data suggest that, without human interference, the current interglacial period would eventually end. Early models anticipated the onset of the next major glacial period to begin within the next 10,000 to 11,000 years.
However, other models focusing on the specific interplay of orbital factors estimate the next natural glacial inception to be around 50,000 years from now. This prediction is based on the idea that the incoming solar energy at 65° N during summer would not decline enough to permit a new glacial period for at least the next 50,000 years.
The Anthropogenic Delay of the Next Ice Age
The natural prediction of the next glacial period is completely overridden by the current state of Earth’s atmosphere, altered by human activity. The industrial-era release of greenhouse gases, primarily carbon dioxide, has effectively disrupted the climate cycle. The concentration of atmospheric carbon dioxide is now significantly higher than it has been for hundreds of thousands of years.
This surplus of heat-trapping gas introduces a powerful warming force that counteracts the subtle cooling trend dictated by the Milankovitch Cycles. The amount of carbon dioxide already emitted is sufficient to suppress the cooling trend for an extended duration, meaning the next major glacial period is being substantially delayed or even prevented entirely.
Climate model simulations show that the carbon dioxide already in the atmosphere will persist, acting as a massive thermal blanket. Due to this persistence, the onset of the next glaciation is now predicted to be delayed by tens of thousands of years, with some projections pushing the event back by 50,000 to 120,000 years. The scale of human-induced climate change has fundamentally altered the planet’s climate trajectory for the foreseeable geological future.