There is little evidence about the Earth’s atmosphere when it was young. However, there is evidence of more recent changes in the atmosphere. Some of this comes from analysis of ice cores drilled in Greenland and the Antarctic.

The ice analysed in these cores has built up over thousands of years as more and more snow fell and was compacted. The deeper the ice, the older it is. Scientists drill down and pull out a long column of ice. The longest is over 3.6 km long. The oldest ice analysed is over 400000 years old, although the Earth is thought to be 4500000000 years old.

There are bubbles of air trapped in the ice from when the snow fell. Scientists have analysed many of these air bubbles to measure the amount of each gas, showing what was in the air at the time the snow fell. The most important information has been about the amount of carbon dioxide in the air. The graph shows data from the ice cores showing how the amount of carbon dioxide in the air has changed over the last 400000 years.

Ice core data showing amount of carbon dioxide in air up to 1950.

1What is trapped in the ice from which measurements about the atmosphere in the past are made?

2Describe in as much detail as you can what has happened to the amount of carbon dioxide in the air over the 400000 years before 1950.

3How could data from other research groups and other places validate this idea?

4Explain why ice core data could not be used to find how much carbon dioxide was in the air when the Earth was young.

5The concentration of carbon dioxide in the atmosphere today is about 0.038%. Comment on this level compared to levels over the last 400000 years.

6Suggest different reasons why carbon dioxide levels have increased in recent years.

7Does this ice core data confirm that humans are causing increasing levels of carbon dioxide? Explain your answer.

Extra challenge

8Suggestwhy ice core data is not used to monitor recent changes in levels of carbon dioxide.

© Pearson Education Ltd 2010. Edexcel GCSE Core Science Activity Pack

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