Which of the following makes ice cores so useful in determining the composition of the atmosphere in the past? A. the presence of pollenthe B. temperature of the core C. air bubbles D. fossilized plants

The correct answer is C: air bubbles.

Explanation:

Analysis of retained gases in ice, through perforations of over 2000 meters deep, has allowed determining the composition of the atmosphere in the past, knowing the CO² atmospheric concentrations and other gases involved in the greenhouse effect for at least 150,000 years. These concentrations have varied in the temporal scale of glaciation, showing low concentrations during glacial periods with low temperatures, and relatively high concentrations during interglacial periods with high temperatures. Between these two periods, abrupt variations on temperature and gas concentration are detected, meaning that changes in CO² cause changes in temperature.  

The increase in CO² is a highly important component in global climatic change and possibly the best documented. This information is the best paleoclimatic documents that complement with others such as marine sediments and tree rings, letting know about the principal traits of terrestrial weather in the lasts 420,000 years, practically four glacial-interglacial cycles.  

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