Identify a primary human-driven cause of modern climate warming.

• A. Burning fossil fuels
• B. Natural orbital changes
• C. Volcanic eruptions
• D. Ocean current shifts

Answer: (A)

The main idea is that human activities are increasing the atmosphere’s greenhouse gases, and that is what drives modern warming. When we burn fossil fuels—coal, oil, and natural gas—we release large amounts of carbon dioxide and other heat-trapping gases. These gases are effective at absorbing infrared radiation, and CO2 stays in the atmosphere for many decades to centuries, so its concentration rises steadily. That boosted greenhouse effect traps more heat near the Earth’s surface, leading to the observed warming.

Natural orbital changes unfold over tens of thousands of years and can’t explain the rapid, long-term warming seen in the last century. Volcanic eruptions tend to inject aerosols that cool the climate for a short time, not produce sustained warming. Ocean current shifts can modulate climate but don’t account for the consistent, human-emission-driven trend. So, burning fossil fuels is the primary human-driven cause of modern climate warming.