D4.3.2—Positive feedback cycles
Positive feedback cycles accelerate climate change when warming triggers processes that release greenhouse gases or increase solar absorption even further.
- Syllabus
- First assessment 2025
- Objective
- D4.3.2
- Level
- SL
Exam analysis
Chance of appearing1%of analysed past papers
Latest appearanceNovember 2025
Most common paperPaper1A
Typical marks1
Common command terms
- Identify
- Explain
Recent exam appearances
November 2025Paper1A ["SL"] · TZ329[ 1 ]D4.3.2—Positive feedback cycles
May 2025Paper1A ["SL"] · TZ230[ 1 ]D4.3.2—Positive feedback cycles
Practice this objective
Coverage 2025–2025 · Updated 16 Jul 2026
Positive Feedback Cycles Amplify Initial Warming
A positive climate feedback produces a change that reinforces the initial warming, making the response larger than the original forcing alone.
| Initial warming causes… | Reinforcing return to warming |
|---|---|
| Deep-ocean CO₂ release | More atmospheric CO₂ strengthens greenhouse forcing |
| Snow and ice loss | Darker surfaces absorb more solar radiation |
| Faster peat/permafrost organic-matter decomposition | More CO₂ is released |
| Permafrost melting | Methane is released |
| More drought and forest fire | Carbon stores burn and forest uptake falls |
Warming melts reflective snow; exposed darker land absorbs more sunlight, causing additional warming and further melt.
Positive means self-reinforcing, not beneficial. Feedback strength and thresholds vary and do not imply one fixed rate of warming.
Positive feedback cycles
Assessment in practice
1 marksHow it is assessed
This objective is assessed through structured response, commonly using Identify / Explain.
Command terms
Identify / Explain
What earns marks
Build the answer around this relationship: Positive feedback reinforces the original warming instead of opposing it.
Representative question
Question 1
Explain how positive feedback cycles could increase the rate of warming of the Earth.
Retrieve the SL Climate Chain
Core D4.3 is secure when every climate impact is explained as a chain: human greenhouse-gas sources or feedbacks change climate conditions, which alter habitats, oceans, carbon stores, or species distributions. Carbon sequestration is the mitigation chain that stores atmospheric CO2.
- human gases and positive feedbacks amplify warming
- boreal forests, ice habitats, upwelling and reefs shift through specific mechanisms
- species may move poleward, upslope, contract, or lose ice/reef habitat
- afforestation, agroforestry, regeneration and peatland rewetting store CO2
Climate Effects on Ecosystems
Core climate-change transfer answers should not list endangered examples. They should identify the climate driver, explain the physical or chemical mechanism, then state the biological consequence. Use this for greenhouse gases, feedbacks, boreal forests, ice-dependent species, upwelling, range shifts, reefs, and carbon sequestration.
- Link human activities to increased greenhouse gases and enhanced warming.
- Explain ecosystem impacts using mechanisms such as positive feedback, carbon sink/source shifts, habitat ice loss, reduced upwelling, range shifts, bleaching or acidification.
- Explain carbon sequestration by naming the storage pathway in biomass, forests, soils or peatlands.
Concept essentials
- Positive feedback reinforces the original warming instead of opposing it.
- Loss of snow and ice lowers albedo and increases solar energy absorption.
- Thawing organic stores can release carbon dioxide or methane that further strengthens warming.