Environmental Science

The primary gas responsible for the greenhouse effect is carbon dioxide (CO₂). The greenhouse effect is the process by which radiation from a planet's atmosphere warms the planet's surface to a temperature above what it would be without its atmosphere. Carbon dioxide, a key greenhouse gas, traps heat in the atmosphere, contributing significantly to global warming and climate change.

Other options: Oxygen and Nitrogen are abundant gases in the Earth's atmosphere but do not contribute significantly to the greenhouse effect because they do not absorb thermal infrared radiation. Hydrogen is a light element and does not play a substantial role in the Earth's greenhouse effect.