Biology · D Continuity and change. The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.
Human activities have raised the concentrations of carbon dioxide and methane in the atmosphere. Both are greenhouse gases, so the Earth is warming. A correlation between carbon dioxide and temperature does not prove the cause by itself. Other evidence, such as the known properties of these gases, shows the link is causal.
Warming can speed itself up through positive feedback: a result of warming causes more warming. This may push ecosystems such as boreal forests and coral reefs past tipping points.
Living things are affected as habitats change. Sea ice is lost, nutrient upwelling is reduced, and species shift their ranges towards the poles or up mountains. Storing carbon in forests and peat (carbon sequestration) can reduce the problem.
Students treat positive feedback as a good effect. Here positive means the change is made larger: warming causes something that leads to more warming.
Answer: The effect of warming (less ice) causes more warming, so the change is amplified. This is positive feedback.
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