Unlocking Earth’s climate secrets from ancient ice

Deep in the polar regions, scientists are drilling into glaciers and ice sheets to study the past. These long cylinders of ice, known as ice cores, contain tiny bubbles and particles that hold a record of Earth’s climate history. Some of this ice is more than a million years old. By studying it, scientists can learn how the climate has changed over time—and what it might do in the future.

How ice cores work

When snow falls, it slowly builds up in layers. Over time, the snow is compressed into ice. As this happens, air and particles from the atmosphere are trapped inside. These include dust, pollen, volcanic ash, smoke, and even tiny amounts of greenhouse gases like carbon dioxide and methane. Ice cores let scientists study these trapped materials and understand the world as it was thousands—or even millions—of years ago.

Each layer of ice tells a story. The deeper the layer, the older it is. Scientists can study these layers to find out what the temperature was like, what gases were in the air, and what natural events happened at that time. This includes volcanic eruptions, wildfires, and dust storms.

Please also read: How Greenland already lost 2 billion tons of ice in one day

Drilling for climate clues

Since the 1960s, researchers have collected ice cores from Greenland, Antarctica, and high mountains around the world. Special drills help them cut deep into the ice. These drills bring up long sections of ice, which are then kept frozen in special storage facilities. Some ice is sent to laboratories where experts carefully study its contents.

One important way scientists study past temperatures is by looking at oxygen in the ice. Water molecules contain different types of oxygen atoms, called isotopes. These isotopes change depending on how warm or cold it was when the snow fell. By comparing the ratios of these isotopes, researchers can estimate ancient temperatures.

Carbon also helps tell the story. A special kind of carbon, called carbon-14, breaks down over time. Fossil fuels like coal and oil have no carbon-14 left. When we burn these fuels, we add “old” carbon to the atmosphere. Ice cores show that the amount of carbon dioxide in the air today is much higher than it was at any time in the last 800,000 years—and much of it comes from burning fossil fuels.

A race to discover the oldest ice

In Antarctica, a group of scientists from the Beyond EPICA project has been drilling deep into the ice at a place called Little Dome C. Their goal: find ice that is over a million years old. This region is ideal because the ice there has stayed still and untouched for a very long time. It took years of searching, radar surveys, and hard work in freezing temperatures, but in January 2025, the team reached bedrock and brought up ice that is 1.2 million years old—the oldest ever recovered.

These ancient ice cores are full of climate secrets. Every meter of ice can hold information about 15,000 years of Earth’s past. By studying the gases and particles in this ice, scientists hope to better understand how Earth’s climate worked in the past and how it might change in the future.

Why this matters today

You might wonder—if the Earth was warmer in the past, why worry now? The answer lies in speed and stability. In the last 11,000 years, Earth’s climate has been unusually stable. This stability allowed humans to build cities, grow food, and create modern civilization. But in just the last few hundred years, greenhouse gas levels and temperatures have started rising fast—faster than at almost any other time in Earth’s history.

Ice cores show us that today’s levels of carbon dioxide are far higher than in the past. They also show that such changes have never happened so quickly. This rapid shift is linked to human activity, especially the burning of fossil fuels.

By looking back into deep time, ice cores help us prepare for the future. They are a warning, but also a tool. The more we understand about how Earth’s climate responded to past changes, the better we can predict—and hopefully reduce—future risks.

Conclusion

Ice may seem simple, but inside it holds a detailed archive of Earth’s history. Thanks to the work of scientists drilling in extreme conditions, we are learning more every year. From bubbles of ancient air to the ashes of long-ago volcanoes, ice cores connect us to the past—and help guide us toward a more stable and sustainable future.