Scientists know a lot about ancient Earth's climate because of clues that remain in rocks, ice, trees, corals, and fossils. These clues tell us that the
Earth's climate has changed many times over the years. There have been times when most of the planet was covered in ice, and there have also been
much warmer periods. Over at least the last 650,000 years, temperatures and carbon dioxide levels in the atmosphere have increased and decreased in
a cyclical pattern