Why Study Past Climate?

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    • The study of ancient climate is key to understanding how the climate system works--and how it might change in the future. Geologic records going back millions of years show that natural patterns, like shifts in Earth's orbit, can steer dramatic changes. 

      These records reveal that carbon dioxide (CO2) and warming are closely linked, and that natural forces cannot account for the changes taking place today. Atmospheric CO2 is now higher than at any time in the past 800,000 years, and probably in the past three million years. And it continues to rise rapidly.

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Deep-sea sediment core

Deep-sea sediment core

Around 56 million years ago, thousands of gigaton of carbon entered Earth's atmosphere in roughly 20,000 years, causing global temperatures to rise 4-5 degrees C (7-9 degrees F).