Which gas leads to increase in global temperature?

Question

Accepted Answer

The correct option is (1):
Carbon Dioxide (CO$*{2}$) is the primary greenhouse gas responsible for the increase in global temperature, a phenomenon known as global warming. CO$*{2}$ works by absorbing infrared radiation (heat) emitted from the Earth’s surface and re-radiating it back, effectively trapping heat in the lower atmosphere. This process is the greenhouse effect. Since the Industrial Revolution, human activities, primarily the burning of fossil fuels (coal, oil, and natural gas) for energy, have released enormous amounts of stored carbon into the atmosphere as CO$*{2}$, significantly enhancing the natural greenhouse effect. This increased concentration of CO$*{2}$ strengthens the heat-trapping capacity of the atmosphere, leading directly to the observed rise in global average temperatures. Although other gases are also greenhouse gases, CO$\_{2}$ is the most significant contributor to climate change due to its sheer volume, persistence, and long atmospheric lifetime.

The incorrect option is (2):
Oxygen (O$*{2}$) is essential for life and is the second most abundant gas in the Earth's atmosphere, but it is not a greenhouse gas. Oxygen molecules, being diatomic and symmetrical, do not absorb long-wave infrared radiation effectively, meaning they do not trap heat and thus do not contribute to the greenhouse effect or global temperature increase. Instead, O$*{2}$ plays a vital role in balancing the atmosphere through natural cycles like respiration and combustion. Therefore, an increase in O$\_{2}$ concentration would not lead to global warming.

The incorrect option is (3):
Ozone (O$*{3}$) is indeed a greenhouse gas and can trap heat in the troposphere (lower atmosphere), contributing to warming. However, the ozone layer in the stratosphere (upper atmosphere) actually protects the Earth by absorbing harmful ultraviolet radiation. While tropospheric ozone is a pollutant that contributes to warming, it is not the dominant gas causing the *increase* in global temperature compared to CO$*{2}$. The scale and impact of human-released CO$\_{2}$ on global temperature rise far exceed that of lower atmospheric ozone.

The incorrect option is (4):
Nitrogen (N$*{2}$) is the most abundant gas in the Earth's atmosphere, making up about 78% of the air we breathe. Like oxygen, nitrogen is a diatomic molecule and is not capable of absorbing significant amounts of infrared radiation. Therefore, N$*{2}$ does not exhibit greenhouse properties and plays no direct role in trapping heat or increasing global temperature. It is considered an inert background gas in the context of the greenhouse effect and global warming discussions.