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Ice Ages: Causes and History Explained

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What an Ice Age Is

A long-term period of significantly reduced global temperature, typically resulting in the expansion of ice sheets and glaciers across large portions of the Earth's surface, lasting anywhere from thousands to millions of years.

Glacial vs. Interglacial Periods

Within a broader ice age, temperatures actually cycle between colder "glacial periods," when ice sheets expand significantly, and warmer "interglacial periods," when ice sheets retreat β€” Earth is currently believed to be in an interglacial period.

Milankovitch Cycles

Long-term, cyclical variations in Earth's orbit and axial tilt that gradually change how much solar energy different parts of the planet receive, widely considered a primary driver behind the timing of glacial and interglacial cycles.

Other Contributing Factors

Beyond orbital changes, factors such as shifting continental positions, volcanic activity, ocean current patterns, and atmospheric greenhouse gas concentrations also play significant roles in triggering and ending ice ages.

Major Ice Ages in Earth's History

Scientists have identified at least five major ice ages throughout Earth's geological history, with the most recent one, the Quaternary Ice Age, beginning roughly 2.6 million years ago and technically still ongoing.

Are We Currently in an Ice Age?

Technically yes β€” since permanent ice sheets still exist at the poles today, Earth is considered to still be within the broader Quaternary Ice Age, currently experiencing one of its warmer interglacial periods.

Why we are technically living in an ice age right now

It often surprises people to learn that, by the scientific definition used by geologists, Earth is technically still within an ice age today β€” the Quaternary Ice Age that began roughly 2.6 million years ago β€” simply because it currently happens to be in one of its comparatively warmer interglacial phases, a period we are living through right now.

Frequently Asked Questions

How long do interglacial periods, like the one we are currently in, typically last?

Past interglacial periods have generally lasted somewhere between about 10,000 and 30,000 years, and the current interglacial period has already lasted roughly 11,700 years, though scientists cannot precisely predict exactly when or how the current cycle will eventually change.

Are current human-caused climate change and natural ice age cycles the same thing?

No β€” they operate on entirely different mechanisms and timescales; natural glacial-interglacial cycles unfold gradually over many thousands of years due to orbital and other slow-moving factors, while current human-caused climate change involves a comparatively rapid rise in temperature over just decades, primarily driven by greenhouse gas emissions.