The red line on graph below shows how levels of carbon dioxide in the Earth's atmosphere have changed through geologic time. The values on the graph's y-axis are measured in parts per million (ppm).

Question

Which of the following statements about the information in the graph is most likely to be true?
A.
During the Carboniferous geologic period, carbon dioxide levels reached their highest point in geologic history.
B.
During the Permian geologic period, the amount of carbon dioxide in the atmosphere increased due to natural processes.
C.
Human activities contributed to the increase in carbon dioxide levels that occurred during the Jurassic geologic period.
D.
Carbon dioxide levels are higher today than they have been at any other time in geologic history.

Answer 1

Based on the information you've provided regarding carbon dioxide levels in the Earth's atmosphere over geologic time, the most likely true statement is:

B. During the Permian geologic period, the amount of carbon dioxide in the atmosphere increased due to natural processes.

This statement aligns with geological understanding that during the Permian period, various natural processes (such as volcanic activity and the formation and breakdown of certain carbon reservoirs) contributed to fluctuations in atmospheric CO2 levels.

The other statements can be evaluated as follows:

A. This is likely false; the Carboniferous period is known for lower CO2 levels, while higher levels occurred at different times in the geological record.

C. This is misleading, as human activities significantly contribute to today's CO2 levels but did not exist during the Jurassic period.

D. This is likely true in light of recent data, but assertions about historical ranges need precise reference to the specific levels at different times in history, which the statement does not confirm without the graph's data.

Without more specific data from the graph itself, the most sound and scientifically supported choice is B.