5.19—Climate models and extrapolation

Extrapolating existing data allows models to project how climate variables may change under specified emissions and human-activity scenarios. The output is conditional on the assumptions, not a guaranteed forecast.

Models support planning, such as flood defences or emissions reduction, by showing how outcomes differ between pathways. Uncertainty comes from future behaviour, incomplete processes, feedbacks and possible tipping points.

A high-emissions pathway may produce more warming than rapid mitigation, but the comparison is meaningful only if both scenarios and their assumptions are stated.

A model range does not mean scientists know nothing, and one scenario is not a prediction of what must happen. Do not treat extrapolation beyond observed conditions as certainty.