Swift and HST COS broadband rms variability spectra of NGC 5548 for selected periods in 2013 (top panel) and 2014 (bottom panel). The XRT data are shown in blue circles and the UVOT data in red circles. The HST COS data (available only for the 2014 period) are displayed in green squares in the bottom panel. The overall rms variability model generated from the variability of all the parameters derived from our spectral modelling (Sect. 3 and Fig. 4) is over-plotted in solid black line on the data. The rms variability of individual model components are also over-plotted in the panels for comparison: comt in blue dotted line, pow in brown dotted line and the obscurer C_f in dashed magenta line. The calculation of the rms spectra are described in Sect. 4. The axes ranges in both panels are identical.