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The climate of the past

By drilling a hollow tube up to 3,000 metres into the Antarctic ice, scientists can pull out samples of ice known as ice cores that have been buried for thousands of years.

Ice cores

Each layer of an ice core represents a particular point in time. The layers contain pockets of ancient air sealed in tiny bubbles that show different concentrations of gases. By studying the archive of gases in the trapped air, scientists can get a very good idea of what the air quality and climate was like up to 900,000 years ago. They may even find clues about future changes that could affect us all.

Click here to download a Word file containing the information from the ice cores


By measuring carbon dioxide concentrations trapped in the ice, scientists now know carbon dioxide concentrations today are the highest for 650,000 years. Scientists have linked these higher concentrations with higher temperatures, suggesting global warming.


After an all-time high in the 1980s, samples of ice from recent years show a drop in lead concentrations in the ice. This shows the impact of the worldwide introduction of lead-free petrol.


Ice layers show a drop in the amount of radioactive gases in the ice following the ban on testing atomic bombs in 1963.


Higher concentrations of carbon dioxide and nitrous oxides trapped in the ice mark the beginning of the Industrial Revolution and the burning of fossil fuels in power stations, factories and cars.


The rise in sodium in the ice marks a time when seas were stormier, throwing up salt onto the ice. Some scientists think that these stormier times mark ‘the Little Ice Age’, a period of much cooler temperatures that lasted until the 1900s.

12,000 years ago:

Thinner layers of ice show that in just a few years, temperatures dropped dramatically. This chill then lasted for another thousand years! From this, scientists have worked out that climate changes can be quicker than previously thought.

73,000 years ago:

Dust and ash in the layers of ice show evidence of a huge volcanic eruption in Indonesia, the biggest of the last 500,000 years. As dust and ash blocked out the sun, the eruption probably cooled global temperatures for many years.

900,000 years ago:

From the deepest ice core samples ever extracted, scientists have confirmed that in the last 740,000 years, Earth has been through eight separate Ice Ages, when the climate was much colder than today.

Extracting an ice core
Working with an ice core