"The BBC, Britain's Meteorological Office, Oxford University, and the University of California at Berkeley on Tuesday launched a program, and software, to mobilize idle time of home computers to better predict climate change," reports TechWeb News.
It's using Windows 2000/XP screensaver software "produced by the BOINC (Berkeley Open Infrastructure for Network Computing) Project, the same group which created the SETI@home software." There's also code for Linux but not Mac OS X.
For more info and to download the software, go to http://bbc.cpdn.org/
The BBC's FAQ says "You are advised not to run the experiment on a laptop." Because it's processor-intensive, there are potential overheating problems.
Update: The BOINC site says: "The experiment is described on a BBC television documentary Meltdown (BBC-4, February 20th, for UK BOINCers). Simplified client software is available at bbc.co.uk/climatechange. Experienced BOINCers can attach to http://bbc.cpdn.org (check out the new graphics!). "