Ice cores are cylinders of ice drilled out of an ice sheet or glacier
One method of dating ice cores is to count the layers in the ice.
The ice contains small bubbles of air which are samples of the atmosphere from the time they were trapped. Scientists can use carbon dating on the carbon dioxide in these air bubbles. This allows the ice to be dated.
It is possible to measure the past concentration of gases.
Research on Ice cores shows that:
- Atmospheric carbon dioxide levels are now 40% higher than before the Industrial revolution. This increase is thought to be due to the burning of fossil fuels and deforestation.
- There has been a huge increase in the amount of methane in the atmosphere over the last two centuries, due to the intensive livestock farming, rice paddies and landfill.