- from Climate
What was the climate like 18,000 years ago? Amazingly, scientists actually know.
They’ve gathered clues from rocks, fossils, ancient ice, and ocean sediment and put them together to form a picture of the last great ice age, when glaciers pushed down into what is now the United States.
Scientists can go a lot further back than that, though. Using similar clues, they’ve tracked rising and falling global temperatures over the past billion years.