CAP Environmental Science Fundamentals 3 — Questions and Answers
Question 1: Which greenhouse gas has the highest 100-year Global Warming Potential (GWP) among those commonly tracked in carbon inventories?
- Carbon dioxide (CO₂)
- Methane (CH₄)
- Nitrous oxide (N₂O)
- Sulfur hexafluoride (SF₆) (Correct answer)
Correct answer: Sulfur hexafluoride (SF₆)
SF₆ has a 100-year GWP of approximately 23,500, far exceeding CO₂ (1), CH₄ (28-36), and N₂O (265-298).
Question 2: What is 'albedo' in the context of Earth's energy balance?
- The heat capacity of ocean water
- The reflectivity of a surface to incoming solar radiation (Correct answer)
- The rate of infrared emission from land surfaces
- The transparency of the atmosphere to visible light
Correct answer: The reflectivity of a surface to incoming solar radiation
Albedo is the fraction of incoming solar radiation reflected by a surface; high-albedo surfaces (like ice) reflect more energy, while low-albedo surfaces (like oceans) absorb more.
Question 3: The concept of 'planetary boundaries' primarily helps scientists understand what?
- The maximum altitude at which aircraft can operate safely
- Safe operating limits for Earth systems beyond which risks increase sharply (Correct answer)
- The boundary between terrestrial and oceanic carbon stocks
- Legal boundaries for cross-border carbon trading
Correct answer: Safe operating limits for Earth systems beyond which risks increase sharply
Planetary boundaries define the safe operating space for humanity by identifying Earth system thresholds; crossing them risks abrupt or irreversible environmental changes.
Question 4: Which process converts atmospheric nitrogen into forms usable by plants, supporting ecosystem productivity?
- Denitrification
- Nitrification
- Biological nitrogen fixation (Correct answer)
- Atmospheric deposition
Correct answer: Biological nitrogen fixation
Biological nitrogen fixation by bacteria (e.g., Rhizobium) converts inert N₂ gas into ammonia (NH₃), which plants can incorporate into amino acids and proteins.
Question 5: In ecosystem science, what does 'net primary productivity' (NPP) measure?
- Total solar energy captured by vegetation
- Carbon fixed by plants minus carbon lost through plant respiration (Correct answer)
- Total carbon stored in soil organic matter
- The ratio of photosynthesis to decomposition in a biome
Correct answer: Carbon fixed by plants minus carbon lost through plant respiration
NPP represents the net carbon gain by vegetation — gross photosynthesis minus autotrophic (plant) respiration — and indicates how much carbon is available to the food web.
Question 6: Which phenomenon explains why Arctic regions are warming approximately 2-4 times faster than the global average?
- Increased methane hydrate release alone
- Polar vortex disruption reducing cloud cover
- Ice-albedo feedback amplifying warming (Correct answer)
- Reduced ocean currents delivering less cold water
Correct answer: Ice-albedo feedback amplifying warming
As Arctic sea ice melts, it exposes darker ocean water with lower albedo, which absorbs more solar energy and accelerates further warming — a powerful positive feedback loop.
Question 7: What is the approximate pre-industrial baseline concentration of CO₂ in Earth's atmosphere?
- 180 ppm
- 280 ppm (Correct answer)
- 350 ppm
- 415 ppm
Correct answer: 280 ppm
Pre-industrial CO₂ concentration was approximately 280 ppm; current levels have exceeded 420 ppm, representing a roughly 50% increase driven by human activities.
CAP Environmental Science Fundamentals 3
Which greenhouse gas has the highest 100-year Global Warming Potential (GWP) among those commonly tracked in carbon inventories?