Many scientific advances have been made toward accurately collecting evidence for global climate change. Explain one technique used: (1 ) to measure changes that have occurred in atmospheric CO2 over the past 500,000 years; and (2 ) to measure the

Question

long-past temperatures over this same period of time.

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Answer 1

(1 ) Atmospheric CO2 has been measured for time-frames going back 500,000 years by analyzing bubbles of air trapped in Antarctic ice cores. It has been found that CO2 concentrations were low during cold glacial period and high during warm interglacial periods; however, overall CO2 levels remained below 300 ppm throughout this time, until the Industrial Revolution, when CO2 began to increase to its current level of 388 ppm.
(2 ) Temperature measurements have been estimated by examining deep-sea sediment cores and measuring the relative amounts of hydrogen and oxygen isotopes in these cores. The same isotope ratios are reflected in the fossilized bodies (shells) of organisms found in these sediments. Using established relationships between isotope ratios and water temperature, temperature changes over a 300,000 period have been able to be determined.