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Volume I · MMXXVI AP Environmental Science
Library› AP Environmental Science› Unit 9: Global Change
⁂   AP Environmental Science · Unit 9

9. Global Change

15–20% of the AP exam. 15 key topics. 4 common errors analyzed.

15–20% exam weight

Unit 9: Global Change

Unit 9 (Global Change) addresses environmental systems and human impacts. FRQs in this unit typically ask you to identify problems, propose specific solutions, and explain environmental consequences.

Key topics in this unit

  1. Stratospheric ozone depletion: CFCs as catalytic destroyers of ozone
  2. Ozone depletion chemistry: CFC photolysis and halogen chain reactions
  3. Montreal Protocol (1987): international response to ozone depletion
  4. Greenhouse effect mechanism: solar radiation absorption and infrared re-emission
  5. Major greenhouse gases: CO2, CH4, N2O, water vapor, CFCs
  6. Anthropogenic sources of greenhouse gas emissions
  7. Climate change impacts: sea level rise, glacial retreat, extreme weather
  8. Ocean warming and coral bleaching
  9. Ocean acidification: CO2 + H2O → H2CO3 chemistry and impacts on marine organisms
  10. Climate feedback loops (ice-albedo feedback, permafrost methane release)
  11. Invasive species: pathways, ecological impacts, and management
  12. Endangered species and extinction drivers (HIPPO framework)
  13. CITES (1973): international wildlife trade regulation
  14. Endangered Species Act (ESA, 1973): US domestic protections
  15. Human impacts on biodiversity: habitat loss, overexploitation, pollution, climate change

Common errors — what the rubric penalizes

These are the most frequently penalized mistakes on AP exam FRQs and MCQs. Review each before your next practice session.

Common error

Confusing the greenhouse effect (infrared re-emission by atmospheric gases trapping heat — a natural and necessary process) with enhanced greenhouse effect (amplification of that process by anthropogenic emissions driving climate change) — framing the greenhouse effect as inherently harmful misrepresents the science

Common error

Conflating ozone depletion (stratospheric ozone destroyed by CFCs, increasing UV-B radiation) with climate change (enhanced greenhouse effect raising surface temperatures) — they share some GHGs but are distinct mechanisms with different geographic and chemical drivers

Common error

Misidentifying mitigation vs. adaptation strategies: mitigation reduces or prevents greenhouse gas emissions (e.g., switching to renewables, carbon capture); adaptation adjusts human or ecological systems to the consequences of climate change already occurring (e.g., building seawalls, drought-resistant crops) — the distinction is frequently tested on FRQ solution-proposal questions

Common error

Stating that the Montreal Protocol addressed climate change rather than ozone depletion — it is a treaty targeting CFC phase-out to protect stratospheric ozone, not a climate agreement; the Paris Agreement addresses climate change

Study checklist

  • Can you list all key topics from memory without this page?
  • Have you worked through at least one FRQ-style question per topic?
  • Can you explain each common error above — and why the correct answer differs?
  • Have you reviewed the relevant College Board CED section and formula sheet entries?
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Our worked solutions and practice questions are original instructional content created by Tian2 AP. They are aligned to the concepts and skills described in College Board’s Course and Exam Description and are not reproductions of, or affiliated with, College Board’s official materials.