How has Earth's climate changed? How fast are levels of carbon dioxide and other greenhouse gases increasing by, and how do these levels compare with past changes in the planet's atmosphere?

The answers lie in the ice.

What can ice tell us about climate change?

Antarctica has been covered by ice for at least the last six million years. That means that snow that fell hundreds of thousands of years ago is still there, compacted and crushed into layers of ice.

These ice layers can tell us a lot about what the Earth was like when they first formed. By studying them, scientists can work out what the climate conditions were like far back in time, from ice thickness to global temperatures.

Bubbles trapped in the ice can even tell us what the air was like hundreds of thousands of years ago. They can reveal the amount of greenhouse gases in the atmosphere for example, or the kind of pollutants released that year.

Ice is like the Earth's hard drive. Each year that snow falls, the ice compacts and another layer of information is recorded. 

But how do we extract this information?

What is an ice core?

A sample of a drilled ice core in the process of being cut
A sample of a drilled ice core in the process of being cut (photo courtesy of British Antarctic Survey)

An ice core is a cylinder of ice drilled out of an ice sheet or glacier.

On the polar ice sheets of Greenland and Antarctica, scientists can extract ice cores up to 3km deep, taking us back 123,000 years in Greenland and over 800,000 years in Antarctica.

Each layer of an ice core is derived from snow that fell at a certain time in the past, and each layer is like a time capsule, containing information about what the atmosphere was like at the time the snow fell

Discovering Antarctica

Antarctic ice cores show us that the concentration of carbon dioxide was stable over the last millennium until the early 19th century.

It then started to rise. Now its concentration is now nearly 40 per cent higher than it was before the Industrial Revolution.

An infographic showing the atmospheric changes that can be captured in ice cores
(infographic courtesy of British Antarctic Survey)

 

 

 

Ice cores can also help us identify more recent changes in the Earth's atmosphere, such as the radioactive material released during nuclear testing in the 1950s, or the results of introducing unleaded petrol in the 1980s.

A serene seascape sketch with calm waters and an orange tint to the sky

Our Ocean, Our Planet

Our Ocean, Our Planet is a new online space at Royal Museums Greenwich dedicated to exploring the climate crisis and our relationship with the ocean