Question

1. many periods of global warming have occurred during the last 100,000 years. the inferred primary cause of the current rise in global temperatures is the

a) change in the eccentricity of earths orbit
b) change in position of tectonic plates
c) increase in atmospheric greenhouse gases
d) increase in sunspot activity

Explanation:

• Option A: Changes in Earth's orbital eccentricity occur over very long - term (tens of thousands of years) and are not the main cause of the recent (last few decades - century) global warming.
• Option B: Tectonic plate movements affect geological processes (such as mountain building, volcanic activity in some cases) over millions of years and have no direct relation to the current global temperature rise.
• Option C: Human activities (such as burning fossil fuels, deforestation) have led to a significant increase in atmospheric greenhouse gases (e.g., carbon dioxide, methane). Greenhouse gases trap heat in the Earth's atmosphere, which is the primary cause of the current global warming trend.
• Option D: Sunspot activity has a cyclical pattern, but scientific evidence shows that the increase in global temperatures cannot be attributed to changes in sunspot activity. The warming trend is inconsistent with the cyclical nature of sunspot activity, and the magnitude of temperature change due to sunspot activity is much smaller than the observed recent warming.

Answer:

C. Increase in atmospheric greenhouse gases