Feedbacks in the Earth System
- Earth & Space
- Ages 14–18 · Grades 9–12
What you’ll find out
- Positive (amplifying) feedbacks, such as ice–albedo and water vapour, reinforce change.
- Negative (stabilising) feedbacks, such as the rock-weathering thermostat, oppose change.
- Stabilising feedbacks are too slow or too weak to offset rapid human emissions.
No sign-up and no real names. In the lesson you check your understanding as you read, and practise until it sticks.
Amplifying feedbacks
Earth’s air, water, ice, rock and living things are connected. So a change in one part triggers changes in others. When the response strengthens the original change, it is called a positive, or amplifying, feedback. A key example involves ice. Bright ice and snow reflect most sunlight back to space. As the Arctic warms and sea ice melts, darker ocean water is exposed. The dark water absorbs far more sunlight. The region warms further, and more ice melts. This helps explain why the Arctic is warming so quickly. Similarly, a warmer atmosphere holds more water vapour, itself a greenhouse gas, which adds to the warming.
Stabilising feedbacks
Other feedbacks oppose the original change, helping to keep the system stable. These are called negative, or stabilising, feedbacks. One operates through rocks. When the climate warms, evaporation and rainfall increase. That speeds up the chemical weathering of rocks such as granite. The weathering reactions consume carbon dioxide from the atmosphere. The carbon is eventually locked into limestone on the sea floor. Less carbon dioxide means less warming. This feedback has helped keep Earth habitable for billions of years. But it is extremely slow, working over hundreds of thousands of years rather than centuries. The oceans also absorb about a quarter of our carbon dioxide.
Curriculum links: NGSS HS-ESS2-2 · England KS4: Chemistry · Cambridge IGCSE: Environmental Management · NCERT Geography, Class 11