The greenhouse effect can be described as what?

• A. Entirely natural, with no human influence
• B. A natural phenomenon that has been enhanced by human activity
• C. Caused solely by volcanic activity
• D. A modern myth

Answer: (B)

The greenhouse effect is a natural warming process where certain gases in Earth's atmosphere trap heat radiating from the surface, keeping the planet warmer than it would be otherwise. This natural mechanism provides a stable climate that supports life.

Human activities have increased the concentrations of these greenhouse gases—like carbon dioxide, methane, nitrous oxide, and various fluorinated gases. That extra gas traps more heat, boosting the effect and causing additional warming beyond natural levels. So the best description is that it’s a natural phenomenon that has been enhanced by human activity.

It isn’t purely natural, because the current amount of warming tracks closely with the rise in human-emitted greenhouse gases. It isn’t caused by volcanic activity alone, which contributes only modest additional CO2 on top of ongoing human emissions. And it isn’t a modern myth, since extensive measurements and analyses show that the enhanced greenhouse effect is real and responsible for much of recent climate warming.