In this paper I address in a general sense the physical sciences issues that need to be tackled to be able to assess the social-economical impacts of adaptation and mitigation with respect to changing extreme events. In particular I will focus on drought as an example. The above by all means does not imply that the social sciences are not relevant on the contrary but being a physical scientist I limit myself to the area I consider myself best suited to address.

A very important part in assessing what the social-economical impacts of adaptation and mitigation are is the predictability of the system, how can an extreme event be predicted both with respect to scale (size, magnitude, location etc.) and to time (onset, duration etc.). However, one could also reverse the question and ask what kind of predictability would be needed and how good that predictability needs to be to be able to address the mitigation and adaptation and the consequent impacts on a social-economical area.

For example the prediction of the onset of a particular drought is still very difficult and even when a drought has started its duration cannot be easily predicted. Even though there is consensus that current global change will also change and most likely increase the number and size of extreme events, how that will take shape is far from clear.

There is much experience in monitoring droughts in North America and much research these days is dedicated to improve our understanding of drought processes. Is that increased knowledge necessary and sufficient to address the issues related to adaptation and mitigation to droughts and what the social-economic consequences are? In this presentation I will address several examples and comparisons using case studies to shed some more light on this issue.