Final answer:
Carbon dioxide (CO₂) is the atmospheric gas that helps retain the sun's energy in our atmosphere as a greenhouse gas, playing a pivotal role in the Earth's greenhouse effect and global warming.
Step-by-step explanation:
The atmospheric gas that helps keep the sun's energy in our atmosphere and is a greenhouse gas is Carbon dioxide (CO₂). This gas plays a crucial role in the retention of heat by absorbing and re-radiating infrared (IR) radiation emitted by the Earth's surface, contributing to the natural greenhouse effect. Without such gases, the heat would escape back into space, and the Earth's average temperature would be significantly lower, making the planet much less habitable.Greenhouse gases include carbon dioxide, methane, water vapor, nitrous oxide, and ozone. Since the Industrial Revolution, the concentration of these gases has been on the rise due to various human activities, thus amplifying the natural greenhouse effect and resulting in global warming. Of the gases listed in the question, carbon dioxide is notable for its prevalent role in this process.The correct answer to which atmospheric gas is being described is Carbon dioxide (CO₂), option 2.