Answer:
Scientists now know how much carbon dioxide was present in the atmosphere as far back as 800,000 years ago. How did they obtain this data?
fossil finds
computer models
ice cores
glacier striations
Step-by-step explanation:
Answer Ice Cores
Scientists use several methods to reveal Earth’s climate history. These methods include the study of glacial striations, fossils, and ice cores.
As glaciers move, they trap and drag rocks beneath them. The grooves that result in the underlying landscape are called glacial striations. Glacial striations have been found in areas of the world that are not currently covered in glaciers, but which must have been covered in ice sheets at some point.