Passage III

Greenhouse gases such as methane (CH4) warm Earth's climate. Figure 1 shows the concentration of CH4 in Earth's atmosphere and the solar radiation intensity at Earth's surface for tropical Europe and Asia over the past 250,000 years. As the figure shows, the CH4 concentration and the solar radiation intensity have increased and decreased at the same times over most of this period. Figure 2 shows the same types of data for the same region over the past 11,000 years. This figure is consistent with the hypothesis that the greenhouse gases from human activities may have begun warming Earth's climate thousands of years earlier than once thought.

15. According to Figure 2, if the trend in the CH4 concentration had continued to match the trend in the solar radiation intensity, the CH4 concentration at present would most likely be:

Answer and Explanation

Your Answer is

Correct Answer is A

Explanation

Looking at figure 2, it can be found that the solar radiation curve and the CH4 concentration curve begin to diverge when the abscissa is equal to 5. And if the CH4 curve continues to keep the same trend as the solar radiation curve, it can be seen that when the abscissa is 0 (present), the ordinate of the CH4 curve ( Look at the ordinate on the right) is about 450, so option A is in line