Climate science · systems
Feedback loop
Definition
A feedback loop is a circular causal pathway in which a change in a system triggers processes that feed back on the initial change. A positive (reinforcing) feedback amplifies the disturbance — in climate, the water-vapour feedback (warming air holds more vapour, a greenhouse gas, causing further warming) and the ice-albedo feedback (melting ice exposes darker surfaces that absorb more heat). A negative (balancing) feedback counteracts the disturbance and stabilises the system. The American Meteorological Society defines a climate feedback as an interaction in which a perturbation in one climate quantity causes a change in a second, and the change in the second ultimately leads to an additional change in the first.
References
AMS feedback definition, balancing vs reinforcing loops, water-vapour and ice-albedo examples
Overview
What it means
Feedbacks explain why the climate response to forcing is larger than the direct effect of CO2 alone, and why systems can shift abruptly: when reinforcing feedbacks dominate past a threshold, change can become self-sustaining — the mechanics behind tipping points.
How it is used
Used in climate modelling (feedback factors and climate sensitivity), ecology, economics and systems-thinking analysis of socio-technical transitions.
Why it matters
Feedback strength determines how much warming a given emission trajectory produces and where abrupt-change risks lie; it is the quantitative bridge from emissions to impacts.