Climate Variability and Change—Hydrological Impacts (Proceedings of the Fifth FRIEND World
Conference held at Havana, Cuba, November 2006), IAHS Publ. 308, 2006, 375–381.
GCM and downscaling uncertainty in modelling of current
river flow: why is it important for future impacts?
Christel
Prudhomme
Centre for Ecology and Hydrology, Wallingford, Oxfordshire OX10 8BB, UK
c.prudhomme@ceh.ac.uk
Abstract This paper compares the
uncertainty in flow simulation due to the modelling of precipitation (using
three global circulation Models, GCMs, and two downscaling techniques) with the
current natural flow variability in three catchments in Scotland. The reference
daily flow series, obtained by running a calibrated continuous rainfall–runoff
model with observed catchment rainfall and potential evaporation, is compared
with simulations from a range of different precipitation scenarios,
representative of the climate modelling uncertainty and current natural
variability. Results show that the natural variability can be large and differs
from one catchment to another. The reproduction of climate variability from
different GCMs is not always within this natural variability and there is some
regional variation in the GCMs’ and downscaling techniques’ ability to
reproduce the current climate. The uncertainty due to GCMs is consistently
larger than that of downscaling techniques.
Key words climate change impact; downscaling;
GCM; RCM; SDSM; uncertainty