Fig. 2. Conceptual framework of the challenges posed by different cases
of flood event attribution, including possible solutions.
2.1 Non-linear relation between extreme precipitation and
floods
Shifts in precipitation extremes are not clearly reflected in global
flood observations (Berghuijs & Slater, 2023; Blöschl et al., 2017; Do
et al., 2017; Kundzewicz et al., 2014; Slater et al., 2021; Zhang et
al., 2022). To examine where trends of extreme precipitation and of
extreme discharge converge and diverge in sign, we calculated
significant trends in annual multi-day extreme precipitation based on
the ERA5 climate reanalysis dataset (Harrigan et al., 2020), and in
extreme discharge based on the dataset GloFAS, which is modelled based
on ERA5 meteorological forcing (Hersbach et al., 2020), for the period
1979-2020 (Fig. 3). Although over most locations the sign of trends in
discharge extremes matches that of precipitation extremes (orange and
green colours), for many locations an increase in precipitation extremes
is matched by a decrease in discharge extremes (blue). Locations where
decrease in precipitation extremes is matched by an increase in
discharge extremes (purple) are very rare.