Simple models of glacier dynamics based on volume–area scaling underestimate climate sensitivity and response time of glaciers. Consequently, they may predict a faster response and a smaller long-term glacier loss. These biases in scaling models are established theoretically and are analysed in detail by simulating the step response of a set of 703 Himalayan glaciers separately by three different models: a scaling model, a 2-D shallow-ice approximation model, and a linear-response model.