2012:60 Technical Note, Handling of climate related issues in the safety assessment SR-Site

The application is based on research carried out over several decades and is an impressive compilation of data and knowledge of the site of Forsmark. The sections on climate, glaciations and permafrost have developed continuously through the earlier compilations reported (e.g. the SR-97-reports). Much has been improved over the years while new question marks have occurred and some known weaknesses still remain.

On the general structure there are some remarks on the way the process is described in the proposal. It is unclear how new research findings can enter and influence the decision process. In addition the background data is difficult to find. The reader needs to dig deep down into the archives of SKB to get information.

The climate scenario is a modification of the climate record received by oxygen isotope data from the Greenland ice cores. It is called a reference climate cycle, which is a good naming as the cycle can be multiplied by any number to describe the future. The modification in this reference climate cycle is made by the use of a numerical model of an ice sheet over Scandinavia. This is a pragmatic solution which may improve our understanding of the Weichselian climate. But it is also somewhat problematic as the ice sheet model used for the calibration in turn is driven by the climate curve. The data sets are thus not independent of each other. This makes it very difficult to estimate the accuracy in calculated results, such as permafrost depth. The lack of true error estimations is in general a problem all through the climate related sections. They are consequently underestimated.