IB Biology HL D4.3.2 Positive Feedback Cycles Questions

Analyse how climate warming triggers albedo, greenhouse-gas and ecosystem changes that amplify the original temperature rise.

Exam points

Explain how melting polar ice lowers albedo, increases absorbed radiation and amplifies warming.
Analyse positive-feedback chains in which warming releases greenhouse gases from permafrost, oceans, fires or livestock and accelerates further warming.
Distinguish a self-amplifying climate loop by linking the initial warming, intermediate physical or biological change and resulting greenhouse-gas or radiation increase.

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Study D4.3.2—Positive feedback cycles conceptsOpen the corresponding Concept lesson for explanations, examples and exam connections.

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Average human internal (core) body temperature is $36.4^{\circ} \mathrm{C}$ , with slight variations between day and night. The average surface temperature of the Earth in the 20th century was $13.9^{\circ} \mathrm{C}$ . It has now risen to $14.8^{\circ} \mathrm{C}$ .

Melting polar ice due to global warming is reducing reflection of sunlight from the Earth. Identify with a reason whether this will result in positive or negative feedback.

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a	positive feedback because warming causes melting of polar ice;
b	positive feedback because less ice means less sunlight is reflected (lower albedo);
c	positive feedback because more heat is absorbed by the Earth's surface which becomes warmer;

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IB Biology HL D4.3.2 Positive Feedback Cycles Questions question 1