How can scientists tell what the temperatures and CO2 levels were in the atmosphere thousands of years ago ?
Scientist take ice cores from old ice fields where ice has accumulated undisturbed over thousands of years, such as in Greenland and the Antarctica. They then analyse these cores for clues on temperatures and CO2 content during that time. Passed temperature levels can also be determined by taking readings from tree-rings, fossilised shells of microscopic marine organisms, fossilised pollen grains and lake sediment samples.
