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The Levels of Carbon Dioxide in the Atmosphere

Question 21
Multiple Choice

The levels of carbon dioxide in the atmosphere A) peaked around 1950 and have begun slowly decreasing since then. B) are high but not higher than the highest estimated levels in the last 420,000 years. C) are estimated to be higher than at any time in the past 420,000 years. D) began decreasing when the burning of fossil fuels increased.

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Q 22
The graph below indicates that global temperatures have A) varied randomly over the last 160 years. B) shown no real trend over the last 160 years. C) tended to increase, especially in the last 100 years. D) tended to decrease over the last 160 years.
Q 23
Atmospheric carbon dioxide levels are shown below.This graph was developed by measurements that were obtained in which of the following two ways? A) direct measurements on Mauna Loa, Hawaii, and from air bubbles trapped in ice. B) studies of plant structures in response to differing CO₂ levels and measurements of carbon dioxide within rock layers. C) carbon isotope levels in seafloor sediments and from air bubbles trapped in ice. D) measurements from undisturbed bat droppings in caves on a South Pacific island and carbon isotope levels in sea floor sediments.
Q 24
Greenhouse gases warm the planet by A) absorbing and dispersing solar radiation. B) magnifying the energy of solar radiation. C) producing and emitting infrared radiation. D) absorbing and reemitting infrared radiation.
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