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How is 800,000 years of temperature data determined from ice core samples?

Humans were not around 800,000 years ago to record temperature data. However, analysis of ice cores provides us with records from deep time, allowing scientists to determine Earth's temperature thousands of years ago. How is this possible?

Open the Ice Cores section of the Isotope Ratio Mass Spectrometry Learning Tool.

First, view the CO2 and temperature data by clicking the graph on the first page. Note how temperature has gone through significant changes over Earth's history.

Continue through the rest of the Learning Tool to learn how climate scientists determine historical temperatures through proxy measurements using the isotope ratios of hydrogen and oxygen in water molecules in Antarctic ice cores. At this point, do not be concerned with the intricate details of ice core analysis. Instead focus on the big picture: the importance of variations in ratios of stable (non-radioactive) isotopes of hydrogen and oxygen in water in determining historical temperatures.

Your Turn

Proxies are essential for determining temperatures on Earth before temperature records were kept. However, proxies can also apply to situations beyond the realm of scientific analysis. Proxies are simply indicators of a variable that cannot be directly measured. What are some potential proxies of a community's commitment to the environment?

Click here to show answer
Some proxies of a community's environmental commitment could be the community's use of alternative energy sources; the number of fuel-efficient cars, light bulbs and other appliances; use of synthetic fertilizers on lawns; and so on.

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