Accelerated cooling of a gas turbine

The method involves operating a rotor (8) of a gas turbine (1) at a cooling speed to cool the gas turbine. The cooling speed is controlled as a function of critical temperature and/or time, where the critical temperature is a cooling-air temperature of the gas turbine, temperature of a rotor cover (5) or temperature of a casing section or the rotor. A set of permissible cooling speeds is determined as a set of functions of multiple critical temperatures or multiple temperature differences. An independent claim is also included for a gas turbine comprising a temperature measuring device.