So: The study finds a fingerprint of anthropogenic influences on large scale increase in
precipitation extremes, with
remaining uncertainties — namely that there is still a possibility that the widespread increase in heavy
precipitation could be due to an unusual event of natural
variability.The intensification of extreme rainfall is expected with warming, and there is a clear physical mechanism for it, but it is never possible to completely separate a signal of external forcing from climate
variability — the separation will always be statistical in nature.