A low confidence in climate attribution results mainly from lack of monitoring, lack of
a clear precipitation response, and inconsistency between the direction of reported trends and trends documented in global observational products over the default period.
It seems
clear to me that the sentence is about
responses to a shift from one climate regime, the recent past and present day, to another, with less
precipitation, in the future (it is the IPCC climate change impacts report after all, and they do say `... not necessarily producing gradual changes between the current and the future situation»).