Abstract. The height of storm surges is extremely important for a low-lying country like The Netherlands. By law, part of the coastal defence system has to withstand a water level that on average occurs only once every 10 000 years. The question then arises whether and how climate change affects the heights of extreme storm surges. Published research points to only small changes. However, due to the limited amount of data available results are usually limited to relatively frequent extremes like the annual 99%-ile. We here report on results from a 17-member ensemble of North Sea water levels spaning the period 1950-2100. It was created by forcing a surge model of the North Sea with meteorological output from a state-of-the-art global climate model which has been driven by greenhouse gas emissions following the SRES A1b scenario. The large ensemble size enables us to calculate 10 000 year return water levels with a low statistical uncertainty. In the one model used in this study, we find no statistically significant change in the 10 000 year return values of surge heights along the Dutch during the 21st century. Also a higher sea level resulting from global warming does not impact the height of the storm surges. As a side effect of our simulations we also obtain results on the interplay between surge and tide.

A new set of climate change scenarios for 2050 for the Netherlands was produced recently. The scenarios span a wide range of possible future climate conditions, and include climate variables that are of interest to a broad user community. The scenario values are constructed by combining output from an ensemble of recent General Climate Model (GCM) simulations, Regional Climate Model (RCM) output, meteorological observations and a touch of expert judgment. For temperature, precipitation, potential evaporation and wind four scenarios are constructed, encompassing ranges of both global mean temperature rise in 2050 and the strength of the response of the dominant atmospheric circulation in the area of interest to global warming. For this particular area, wintertime precipitation is seen to increase between 3.5 and 7% per degree global warming, but mean summertime precipitation shows opposite signs depending on the assumed response of the circulation regime. Annual maximum daily mean wind speed shows small changes compared to the observed (natural) variability of this variable. Sea level rise in the North Sea in 2100 ranges between 35 and 85 cm. Preliminary assessment of the impact of the new scenarios on water management and coastal defence policies indicate that particularly dry summer scenarios and increased intensity of extreme daily precipitation deserves additional attention in the near future.

ABSTRACT.. Students who were required to write three short essays for a university level course on photochemistry at the Open university of the Netherlands received either audio-cassette or written feedback on their essays. The students receiving the audio feedback described their experience as personal, enjoyable, complete and clear. Those receiving written feedback described their experience as adequate. The amount of time spent by instructors supplying the feedback differed minimally (Xauai o = 53 minutes per student; X~itten = 49 minutes) with the major difference lying in the amount of time spent in preparation. This difference, possibly attributable to novelty with audio as a mode for feedback, was not significant. The amount communicated to the students with audio feedback (per instructor) was significantly greater than the amount communicated with written feedback. There was no difference in the final grades for the two groups of students.The Open university of the Netherlands (OuN) is an institution for open higher distance learning. It offers university level courses to its students in seven different subject areas. Its students may study when they want to and where they want to. This philosophy of freedom precludes requiring students to be at a certain place at a certain time for lessons or tutoring. This poses a problem for courses in which assignments need to be instructor graded and accompanied by instructor feedback when returned to the student. This problem is compounded by the fact that upper level courses may have as few as one part-time instructor for the whole of the Netherlands. A final problem is the isolation and solitude experienced by students at such an institution for distance education. The students have no structural contact with fellow students and practically no personal contact with the Paul A.

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