Global Warming - Biology

1. Fundamental Concepts

Global warming refers to the long-term increase in Earth's average surface temperature, primarily caused by human activities that release greenhouse gases into the atmosphere. The main driver is the enhanced greenhouse effect, where excess greenhouse gases trap more heat, disrupting Earth's climate system.

2. Key Concepts

Main Greenhouse Gases: Carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O)

Major Human Causes: ① Burning fossil fuels (coal, oil, natural gas) → CO₂ release; ② Deforestation → less CO₂ absorption by plants; ③ Agriculture → CH₄ from livestock, N₂O from fertilizers; ④ Industrial processes.

Consequences: ① Rising global temperatures; ② Melting glaciers and ice caps → sea-level rise; ③ More frequent extreme weather events (heat waves, hurricanes, droughts); ④ Ocean acidification; ⑤Disruption of ecosystems and biodiversity loss.

3. Examples

Example 1 (Basic)

Problem: Which of the following are the major human-caused greenhouse gases in Earth's atmosphere? (Select all that apply.)
A. Carbon dioxide (CO₂)
B. Nitrogen (N₂)
C. Methane (CH₄)
D. Hydrogen (H₂)
E. Oxygen (O₂)

Step-by-Step Solution:

The major human-caused greenhouse gases in Earth's atmosphere are: A. Carbon dioxide (CO₂) and C. Methane (CH₄).
Explanation:
CO₂: This is the most significant greenhouse gas emitted by human activities, primarily from burning fossil fuels and deforestation.
CH₄: This gas has a much higher heat-trapping ability than CO₂ and is released during agriculture (especially from livestock), landfills, and natural gas production.
Other options:
N₂: The most abundant gas in the atmosphere (≈78%), but it is not a greenhouse gas.
H₂: Rare in the atmosphere and not a greenhouse gas.
O₂: O₂ is essential for life, but not a greenhouse gas.

Example 2 (Intermediate)

Problem: Match each human activity with its primary impact on global warming.
Human Activities
A. Burning large amounts of fossil fuels
B. Deforestation
C. Agricultural practices (e.g., rice cultivation, livestock farming)

Impacts
① Increases atmospheric CO₂ levels
② Releases CH₄ and other greenhouse gases
③ Reduces the capacity to absorb CO₂

Step-by-Step Solution:

Understand each activity
A. Burning fossil fuels → mainly releases CO₂ from coal, oil, natural gas combustion.
B. Deforestation → removes trees that absorb CO₂ via photosynthesis.
C. Agriculture → rice paddies and cow digestion produce methane (CH₄); manure management also releases N₂O.
Match to the impacts
① Increases atmospheric CO₂ levels ↔ matches A (burning fossil fuels releases CO₂).
② Releases CH₄ and other greenhouse gases ↔ matches C (rice/livestock emit CH₄; also some N₂O).
③ Reduces CO₂ absorption ↔ matches B (fewer trees → less photosynthesis → less CO₂ uptake).
Final matches: A↔①, B↔③, C↔②

Example 3 (Intermediate)

Problem: True or False: If we plant enough trees, we will no longer need to change our energy systems to stop global warming.

Step-by-Step Solution:

Answer: False
Explanation:
Trees absorb CO₂, which helps reduce global warming, but their capacity is limited. Human activities, especially fossil fuel burning, release far more CO₂ than forests can absorb. To prevent dangerous warming, we need both to reduce emissions and maintain natural carbon sinks. Therefore, even planting many trees is not enough; transitioning to low-carbon energy systems is essential.

4. Problem-Solving Techniques

Link cause to effect: Always connect the specific human activities to their environmental impacts. Example: Burning fossil fuels → CO₂ rise → heat trapped → ice melts → sea levels rise
Identify the main human-caused greenhouse gases: CO₂, CH₄, and N₂O. Be able to distinguish them from abundant non-greenhouse gases like N₂ and O₂.
Evaluate Solutions: Reduce emissions (renewables, energy efficiency); Enhance carbon sinks (forests, wetlands); Technological solutions (carbon capture, low-emission technologies).