43. Which gas does NOT contribute to global warming through its greenhouse effect?
    (1) Nitrous oxide (2) Methane
    (3) Carbon dioxide (4) Nitric oxide

The Greenhouse Effect and Global Warming

The greenhouse effect is a natural process essential for life on Earth. It occurs when gases in the atmosphere absorb and re-emit infrared radiation, trapping heat and keeping the planet warm enough to sustain life. Without this effect, Earth’s average temperature would be much colder, making it uninhabitable for most forms of life.

However, human activities have increased the concentration of greenhouse gases in the atmosphere, intensifying the greenhouse effect and leading to global warming—a rise in Earth’s average surface temperature. This warming has far-reaching consequences, including more extreme weather, rising sea levels, and disruption of ecosystems.

Major Greenhouse Gases

The primary greenhouse gases responsible for global warming include:

• Carbon dioxide (CO₂): Emitted from burning fossil fuels, deforestation, and industrial processes. CO₂ is the most significant long-lived greenhouse gas, accounting for the majority of human-caused warming.

• Methane (CH₄): Released during livestock digestion, rice cultivation, fossil fuel extraction, and waste management. Methane is much more effective at trapping heat than CO₂, but it remains in the atmosphere for a shorter time.

• Nitrous oxide (N₂O): Produced by agricultural activities, industrial processes, and combustion. Nitrous oxide is a powerful greenhouse gas with a long atmospheric lifetime.

Other gases, such as fluorinated gases (F-gases), also contribute to global warming, but they are less abundant than CO₂, CH₄, and N₂O.

Nitric Oxide: A Different Role

Nitric oxide (NO) is a gas that contains nitrogen and oxygen. It is distinct from nitrous oxide (N₂O) and plays a different role in atmospheric chemistry:

• Not a Greenhouse Gas: Nitric oxide does not absorb infrared radiation efficiently and therefore does not contribute to the greenhouse effect or global warming. Its main environmental impact is in the formation of ground-level ozone (smog) and acid rain, not in trapping heat.

• Atmospheric Chemistry: NO is important in reactions that form and destroy ozone in the lower and upper atmosphere. However, it does not act as a greenhouse gas.

Comparing the Options

Let’s review each gas in the context of global warming:

• Nitrous oxide (N₂O):

  • Contributes to global warming: Yes. Nitrous oxide is a powerful greenhouse gas with a high global warming potential.

• Methane (CH₄):

  • Contributes to global warming: Yes. Methane is a potent greenhouse gas, second only to CO₂ in its contribution to human-caused warming.

• Carbon dioxide (CO₂):

  • Contributes to global warming: Yes. CO₂ is the main driver of human-induced global warming due to its abundance and long atmospheric lifetime.

• Nitric oxide (NO):

  • Contributes to global warming: No. Nitric oxide is not a greenhouse gas and does not trap heat in the atmosphere.

Why the Distinction Matters

Understanding which gases contribute to global warming is essential for developing effective climate policies and mitigation strategies. Greenhouse gases like CO₂, CH₄, and N₂O are targeted by international agreements and national regulations aimed at reducing emissions. Nitric oxide, while important for air quality and atmospheric chemistry, is not a greenhouse gas and is not included in these efforts.

Key Takeaways

• Carbon dioxide, methane, and nitrous oxide are major greenhouse gases that contribute to global warming by trapping heat in the atmosphere.

• Nitric oxide (NO) is not a greenhouse gas and does not contribute to global warming through the greenhouse effect.

• The main environmental impact of nitric oxide is its role in forming ground-level ozone and acid rain, not in trapping heat.

• Accurate identification of greenhouse gases is crucial for climate science and policy.

Summary Table

Conclusion

Among the gases listed, nitric oxide (NO) does NOT contribute to global warming through the greenhouse effect. Carbon dioxide, methane, and nitrous oxide are all greenhouse gases that trap heat and drive climate change. Nitric oxide, while important for other atmospheric processes, does not act as a greenhouse gas.

In summary, the correct answer is:
(4) Nitric oxide
This distinction is vital for understanding the causes of global warming and developing strategies to address climate change.