Question

Which of the following statements regarding the Earth's temperature and atmospheric composition is true?

A. The earth has remained at the same temperature for roughly 3 billion years.
B. The earth's temperature has been increasing in the past ~100 years but is now stable and expected to remain so in the next few decades.
C. The earth's atmospheric composition has remained stable over geologic time.
D. The earth's atmospheric concentration of CO₂ has increased in the last 100 years.

Answer 1

The Earth's atmospheric concentration of CO₂ has increased in the last 100 years, and the Earth's temperature has been increasing in the past ~100 years. However, the Earth's temperature and atmospheric composition have not remained constant over billions of years.

Step-by-step explanation:

Statement D is true: The earth's atmospheric concentration of CO₂ has increased in the last 100 years. Direct evidence supports the relationship between atmospheric concentrations of carbon dioxide and temperature: as carbon dioxide rises, global temperature rises. Since 1950, the concentration of atmospheric carbon dioxide has increased from about 280 ppm to 382 ppm in 2006. In 2011, the atmospheric carbon dioxide concentration was 392 ppm.

Furthermore, evidence shows that the Earth's temperature has been increasing in the past ~100 years. The enhanced greenhouse effect, caused by the increase in atmospheric CO₂, has led to an average surface temperature increase of about 0.8°C since 1980.

On the other hand, statements A and C are not true. The Earth's temperature has not remained at the same level for billions of years, and the Earth's atmospheric composition has not remained stable over geologic time. Both temperature and atmospheric composition have changed over time due to various factors.