Identifying Green House Gases (GHGs)

Green House Gases (GHGs) are atmospheric gases that absorb and emit radiation within the thermal infrared range. This process causes the greenhouse effect, leading to warming of the planet's surface.

Let's examine each substance listed to determine if it is considered a Green House Gas:

• Surface ozone ($\text{O}_3$): Surface ozone, also known as tropospheric ozone, is a significant Green House Gas. It is formed in the lower atmosphere through chemical reactions involving pollutants like nitrogen oxides and volatile organic compounds.
• Ammonia ($\text{NH}_3$): Ammonia is not typically classified as a direct Green House Gas. However, it can contribute to climate change indirectly, for instance, by reacting with other atmospheric compounds to form aerosols, which can affect radiation balance, or through nitrogen deposition affecting ecosystems. For the purpose of identifying direct GHGs, ammonia is usually excluded from the primary list.
• Methane ($\text{CH}_4$): Methane is a powerful Green House Gas. It is the second most abundant GHG after carbon dioxide and has a much higher global warming potential per molecule than $\text{CO}_2$ over a shorter timeframe. Sources include natural wetlands, agriculture (like rice paddies and livestock), fossil fuel production, and waste decomposition.
• Carbon monoxide ($\text{CO}$): Carbon monoxide is not a direct Green House Gas because it does not absorb thermal infrared radiation effectively. However, it is an indirect GHG. It influences the atmospheric concentrations of other GHGs like methane and tropospheric ozone because it reacts with the hydroxyl radical ($\text{OH}$), which would otherwise break down methane and ozone.
• Nitrous oxide ($\text{N}_2\text{O}$): Nitrous oxide is a potent Green House Gas with a long atmospheric lifetime. Its main sources include agricultural activities (especially fertilizer use), fossil fuel combustion, and industrial processes. It also contributes to the depletion of the stratospheric ozone layer.

Based on this analysis, the substances from the list that are considered Green House Gases are Surface ozone ($\text{O}_3$), Methane ($\text{CH}_4$), and Nitrous oxide ($\text{N}_2\text{O}$).

Comparing this with the given options, we look for the option that includes A, C, and E.

Summary of GHG Status

The list of identified GHGs is Surface ozone (A), Methane (C), and Nitrous oxide (E). Therefore, the option that lists A, C and E only is the appropriate answer.

Revision Table: Understanding Green House Gases

Additional Information: Key Green House Gases

While the question focuses on a specific list, it's useful to know the main Green House Gases recognized globally:

• Carbon Dioxide ($\text{CO}_2$): The primary anthropogenic GHG. Its concentration has increased significantly since the industrial revolution, mainly from burning fossil fuels.
• Methane ($\text{CH}_4$): A potent GHG, though it has a shorter atmospheric lifetime than $\text{CO}_2$. Significant sources are human activities.
• Nitrous Oxide ($\text{N}_2\text{O}$): Another powerful GHG with a long atmospheric lifetime. Agricultural activities are the largest source.
• Fluorinated Gases: This category includes Hydrofluorocarbons (HFCs), Perfluorocarbons (PFCs), Sulfur Hexafluoride ($\text{SF}_6$), and Nitrogen Trifluoride ($\text{NF}_3$). These are synthetic gases used in various industrial processes and products. They have very high global warming potentials, often thousands of times greater than $\text{CO}_2$, and very long atmospheric lifetimes.
• Water Vapor ($\text{H}_2\text{O}$): Water vapor is the most abundant GHG in the atmosphere. However, its concentration is largely controlled by temperature, creating a feedback loop rather than being a primary driver of climate change in the same way as the other GHGs directly emitted by human activity.
• Tropospheric Ozone ($\text{O}_3$): As discussed, ozone in the lower atmosphere acts as a GHG. Stratospheric ozone (in the upper atmosphere) is beneficial as it absorbs UV radiation, but it has a cooling effect rather than warming.

Understanding which gases are GHGs and their sources is crucial for addressing climate change.