Recently our paper „The rainfall erosivity factor in the Czech Republic and its uncertainty“ has been published in Hydrology and Earth System Sciences. In the paper we compare different sources of uncertainty (kinetic energy calculation, interpolation method, spatio-temporal data coverage and natural variability) within the assessment of the rainfall erosivity factor (R-factor). It is shown, that while the uncertainty can be considerably reduced when rainfall erosivity is related to less variable precipitation characteristics (e.g. coefficient of variation of monthly precipitation) provided sufficient number of stations are available, the confidence intervals around the estimated R-factor remain relatively wide even for long (80 years) records. This uncertainty should be taken into account. The paper is available here.