  We extend Laughlin's magnetic-flux-threading argument to the quantized
thermal Hall effect. A proper analogue of Laughlin's adiabatic magnetic-flux
threading process for the case of the thermal Hall effect is given in terms of
an external gravitational field. From the perspective of the edge theories of
quantum Hall systems, the quantized thermal Hall effect is closely tied to the
breakdown of large diffeomorphism invariance, that is, a global gravitational
anomaly. In addition, we also give an argument from the bulk perspective in
which a free energy, decomposed into its Fourier modes, is adiabatically
transferred under an adiabatic process involving external gravitational
perturbations.
