  We present results for the topological susceptibility at nonzero temperature
obtained from lattice QCD with four dynamical quark flavours. We apply
different smoothing methods, including gradient Wilson flow and over--improved
cooling, before calculating the susceptibility. It is shown that the considered
smoothing techniques basically agree among each other, and that there are
simple scaling relations between flow time and the number of cooling/smearing
steps. The topological susceptibility exhibits a surprisingly slow decrease at
high temperature.
