Warning level (in swedish) 2, SwedenThere are however large uncertainties surrounding how these changes will affect hydrological processes, mainly because of the following issues
- each future projection - with its specific combination of (global and regional) climate models, model properties and emission scenarios - gives a different result
- climate model results have uncertainties and systematical errors that may be small in a climate context but that may magnify in hydrological applications
- the resolution of climate model results may be too coarse for direct assessment of hydrological consequences, for example in urban hydrology
To tackle these issues, activities in the hydrological climate impact research include
- ensemble modelling, where up to 10-15 different climate projections are used to drive a hydrological model (HBV or HYPE) and the result is evaluated in probabilistic terms
- application of a post-processing method called Distribution-Based Scaling (DBS), which modifies raw climate model output based on performance in the control period
- development of statistical methods for downscaling precipitation to sub-grid scales, based on additional data from the climate model such as precipitation type and cloud cover
The research on hydrological climate change impacts is performed in cooperation with a large number of national and international partners, e.g. in large national projects and EU-projects (see right column).
References
- Andréasson, J., Bergström, S., Carlsson, B., Graham, P.L., Lindström, G. (2004) Hydrological change - climate change impact simulations for Sweden. Ambio, 33:4-5.
- Olsson, J., Berggren, K., Olofsson, M., Viklander, M. (2009) Applying climate model precipitation scenarios for urban hydrological assessment: A case study in Kalmar City, Sweden. Atmospheric Research 92:364-375.
- Yang, W., Andréasson, J., Graham, L.P., Olsson, J., Rosberg, J., and F. Wetterhall (2010) Improved use of RCM simulations in hydrological climate change impact studies, Hydrological Research, accepted.