Data Visualisation: The GeoWeb has lowered the bar to visualizing data on the topic of Global warming and explaining the background concepts. Examples include Simon Rogers of the Guardian who is using fusion tables to visualise data on a map. See 34mins 33 seconds into this:
He explains how he can now produce useful map visualizations without needing input from specialist software engineers.
Unfortunately Simon hasn't used fusion tables to visualize global warming data (that I can find), however, fusion tables could easily be used to produce maps such as this other Guardian map: Carbon emissions by local authority in the UK. This kind of visualization has great potential as citizens can use them to make voting decisions by comparing their local authority to the others. Maps are very powerful in this regard.
Concept Visualisation: I've also used Google Earth to help visualise climate change concepts, the below clip is explaining Gaia ideas and I use Google Earth at 1min 13secs into this clip:
Mixed Concept and Data Visualisation: Google promotes the use of Google Earth in good causes via Google Earth Outreach, they have a showcase of climate related outreach projects based in Google Earth (click 'climate' link on the right when you reach the page). The showcase is made up of concept and data visualisations. Some of these are excellent such as the National Snow and ice Data Centre (NSIDC) but others could be designed a lot better e.g. 4 degree warming (my review).
I think the GeoWeb has great potential to inform the climate change debate but at present, it hasn't been nearly as well used and discussed as use of the GeoWeb in emergency aid situations and helping the democratic process (e.g. Ushahidi). Despite having a personal interest in using Google Earth to explain climate change concepts, I think the best potential of the GeoWeb in discussing climate change is not in education but in lobbying politicians to live up to their rhetoric on delivering reductions in carbon emissions. A simple 2D map showing how much carbon dioxide is emitted by region is a fantastic tool to bring politicians and policy makers to account, I wish there were more examples out there of this use.