Hydrological climate impact studies: Uncertainties and new methods


The effect of climate change on water related issues is important knowledge for future planning. Current state-of-the-art to quantify the impact of climate change on water resources and hydrology can provide a wide range of possible changes, which is often deemed the uncertainty.

Although the uncertainties in the beginning of the process ((GCM, RCM ,Fig. 1) are often quantified and studied, uncertainties in the latter part of the process, i.e. linking CM results to hydrological models (HMs) using various bias correction or downscaling methods or uncertainties from the HM itself, through to how results are interpreted and used, are often ignored and are less well understood.

At the same time, communicating this wide range of uncertainties to users leads to uncertainty as to how to use scenarios for planning. FoUh is working to improve the methodology of climate impact research studies, to reduce uncertainties, as well as to produce more useful climate projections for different societal actors.

Climate impact studies done today
Figure 1. Overall picture of how climate impact studies done today Enlarge Image


This research initiative at SMHI strives to take a holistic view of how climate impact studies are done and therefore a more holistic view of the uncertainties in the process and where or how these can be reduced, with a focus on the usability of results for future planning. Specifically:

  • Explore the possibilities to filter ensembles of climate projections to find 'representative runs' which can either (a) represent the spread of the CM or (b) can simulate important aspects of the local climate, or the observed historical changes.
  • Determine the uncertainties associated with bias correction and other downscaling/correction methodologies, including comparing the bias correction with other correction methods.
  • In depth, evaluation of how much  the bias-correction methods retain or change data from climate models and future development based on this.
  • Evaluating the suitability of impact models for climate change studies
  • Improve communication of the current climate impact study results to better guide the user in how these results can be used.
  • Develop new methods for climate impact studies with starting points in inverse impact modelling, hydrological response surfaces and circulation pattern coupling
Inverse climate impact modelling
Figure 2. A possible alternative approach for inverse climate impact modelling Enlarge Image