What term refers to the natural warming of the Earth's surface due to the atmosphere trapping heat, a process that can be intensified by human activities?

• A. The greenhouse effect
• B. The jet stream
• C. The ozone layer depletion
• D. The thermohaline circulation

Answer: (A)

The main concept here is the greenhouse effect—the natural warming of Earth’s surface that happens when greenhouse gases in the atmosphere trap heat. Sunlight warms the surface, which then radiates heat upward; greenhouse gases like carbon dioxide and methane absorb much of that infrared radiation and re-emit it back toward the surface, keeping the lower atmosphere warmer than it would be otherwise. This warming is a normal part of the climate system, but human activities increase the concentrations of these gases, intensifying the heat-trapping and driving additional warming. The other options describe different climate/oceanic processes (a high-altitude wind pattern, ozone loss, deep-ocean circulation) that don’t explain the heat-trapping mechanism being described.