Which gas emission reduces global warming?

Appeared in: UP NHM CHO 7 Sept 2022 (Shift-2)

Explanation

Hydrogen sulfide (H₂S) is not a greenhouse gas; instead, it contributes to a cooling effect.
In the atmosphere, H₂S oxidizes to form sulfur dioxide (SO₂), which then converts into sulfate aerosols.
These sulfate aerosols are microscopic particles that increase the Earth's albedo, or reflectivity.
By reflecting incoming solar radiation back into space, these aerosols cause a net cooling of the planet's surface, counteracting global warming.

Option A: Carbon dioxide is the most significant greenhouse gas contributing to global warming by trapping heat in the atmosphere.
Option B: Carbon monoxide is an indirect greenhouse gas. It does not directly trap heat but contributes to the atmospheric persistence of other greenhouse gases like methane, thus promoting warming.
Option D: Oxygen is a major component of the atmosphere but is not a greenhouse gas and does not have a significant direct role in either global warming or cooling.

Clinical Relevance

Nursing practice connection: Knowing Atmospheric gases and their effect on global temperature helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
While H₂S has a cooling effect on the climate, it is a toxic gas. At low concentrations, it has a characteristic rotten egg smell and can cause eye and respiratory tract irritation.
Carbon monoxide (CO) is a dangerous asphyxiant gas because it binds to hemoglobin with much higher affinity than oxygen, leading to oxygen deprivation, which can be fatal.
Sulfur dioxide (SO₂), the intermediate compound, is a major air pollutant that can worsen respiratory conditions like asthma and bronchitis and contributes to the formation of acid rain.

How to Approach the Question

First, identify the core of the question: it asks for a gas that reduces global warming, meaning it has a cooling effect.
Evaluate each option based on your knowledge of atmospheric science.
Recall that Carbon dioxide (CO₂) is the primary greenhouse gas, so it causes warming. Eliminate this option.
Recall that Carbon monoxide (CO) is an indirect greenhouse gas, so it also contributes to warming. Eliminate this option.
Consider Oxygen (O₂). It is a stable, major component of the atmosphere but is not radiatively active in a way that significantly affects global temperature. It is neutral in this context.
Finally, evaluate Hydrogen sulfide (H₂S). Recall or deduce that sulfur compounds can form aerosols in the atmosphere. These aerosols reflect sunlight, leading to a cooling effect. This makes it the correct answer.

Concept Tested & Keywords

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E6 Parks TextBook of Preventive & Social Medicine part 2 — Subpart B (pp 233-449 of 464) p. 51-53

Practise the full UP NHM CHO 7 Sept 2022 (Shift-2)

Attempt every question from this paper in a timed mock, then review the full solution for each one.