The gas which causes global warming is?

1. Analyze the question

The question asks us to identify which of the listed gases is a primary contributor to global warming. Global warming is the long-term heating of Earth's climate system observed since the pre-industrial period due to human activities, primarily fossil fuel burning, which increases heat-trapping greenhouse gas levels in Earth's atmosphere.

2. Explain the concept

Global warming is caused by the Greenhouse Effect. Certain gases in the atmosphere, known as greenhouse gases, allow sunlight to pass through the atmosphere to warm the Earth's surface, but they prevent the heat (infrared radiation) emitted from the surface from escaping back into space. This trapped heat warms the planet.

• O$_{2}$ (Oxygen): Makes up about 21% of our atmosphere and is essential for respiration; it is not a greenhouse gas.
• CO$_{2}$ (Carbon dioxide): Produced by the combustion of fossil fuels (like petrol, coal, and gas) and deforestation. It is the most significant greenhouse gas contributing to human-induced global warming.
• N$_{2}$ (Nitrogen): Makes up about 78% of the atmosphere and is chemically inert under normal conditions; it does not contribute to the greenhouse effect.
• He (Helium): A noble gas that is chemically inert and does not trap heat in the atmosphere.

3. Show the solution

• Identify the gases: Oxygen, Carbon dioxide, Nitrogen, and Helium.
• Evaluate their properties: Only Carbon dioxide (CO$_{2}$) has the molecular structure that allows it to absorb and re-emit infrared radiation, effectively trapping heat.
• Conclusion: As human activities increase the concentration of CO$_{2}$ in the atmosphere, more heat is trapped, leading to a rise in global temperatures.

4. Identify the answer

The correct gas responsible for global warming among the options provided is Carbon dioxide.

Correct Option: B

5. Tip

When you see questions about "Global Warming" or "Greenhouse Gases," always look for CO$_{2}$, Methane (CH$_{4}$), or Water Vapor. Remember that noble gases (like Helium) and diatomic gases (like N$_{2}$ and O$_{2}$) are generally not responsible for the greenhouse effect because they do not absorb infrared radiation effectively.