Global Warming Statements Analysis

The question asks to identify the correct statement regarding Global Warming.

Evaluating Statement Options

• Statement 1: Water vapour does not contribute to global warming. This is incorrect. Water vapour is a powerful greenhouse gas and a major contributor to the natural greenhouse effect and global warming.
• Statement 2: Global warming is likely to increase the productivity of plants due to $CO_2$ fertilization. This statement is considered correct in many contexts. Increased atmospheric carbon dioxide ($CO_2$) levels can stimulate photosynthesis and growth in many plants, a phenomenon known as the $CO_2$ fertilization effect. While other factors like temperature, water availability, and nutrient levels also influence plant growth, $CO_2$ fertilization is a recognized potential impact of rising $CO_2$.
• Statement 3: CFCs do not cause global warming, but can cause ozone layer depletion in stratosphere. This is incorrect. Chlorofluorocarbons (CFCs) are potent greenhouse gases that contribute significantly to global warming, in addition to depleting the ozone layer.
• Statement 4: HFCs and HCFCs are good substitutes for the ozone depleting substances as they cause neither global warming nor ozone layer depletion. This is incorrect. Hydrofluorocarbons (HFCs) are powerful greenhouse gases and contribute significantly to global warming. Hydrochlorofluorocarbons (HCFCs) also contribute to global warming, albeit less than CFCs, and still cause some ozone depletion.

Conclusion on Correct Statement

Based on the analysis, the statement that accurately reflects a known effect related to increased $CO_2$ levels associated with global warming is the $CO_2$ fertilization effect on plant productivity.

Correct Statement: Global warming is likely to increase the productivity of plants due to $CO_2$ fertilization.