1. Who are the users? The key target group should really be those people at EU, national, regional or local level who are charged with long-term planning decisions or environmental legislation. Richard mentions coastal and water managers - these functions in most countries are usually split between many different agencies which causes problems. Local authorities, especially those in metropolitan areas, should also be seen as a key target group. As far as influencing Framework V is concerned, we have missed the boat, so additional research managers will need to be targeted.
By the way, I'm not convinced by Jan Goudrian's notion of targeting science journalists. There are some really dumb journalists around and although the idea is good to influence and improve the quality of public debate in this area, in the end journalists are about getting or creating a good story and not about the critical process of scientific exploration and reflection.
2. How do we canvass them? This is potentially a huge task and we need to devise some strategy to make it manageable. Inviting voluntary involvement runs into the same problem we faced here in the UK in that only those already convinced of the importance of the issue will get involved. For many other potantial users, they need convincing that there is a real policy issue here, and one that demands their immediate attention. And convincing people of the priority of this issue is not easy - after all, I don't think we really know where climate change impacts should fit in the hierarchy of policy issues, or even in the subset of environmental policy issues.