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.

18. One solar radiation cycle is the time between a maximum in the solar radiation intensity and the next maximum in the solar radiation intensity. According to Figure 1, the average length of a solar radiation cycle during the past 250,000 years was:

Answer and Explanation

Your Answer is

Correct Answer is G

Explanation

Each unit of the abscissa of figure 1 represents 10,000 years, and the abscissa between every two peaks is basically about 2-3 units, so the option of 15000-35000 is the closest