I realise (because of a comment my wife just made on reading my blog) that I've been a bit free with my "WGI"'s in the last post or so. So...
WGI means IPCC working group one. There are three, and you can download the three reports from http://www.grida.no/climate/ipcc_tar/.
When people *say* IPCC, they tend to mean WGI - "The scientific basis". The one about past and future climate changes, etc. The other two are less well known: WGII is "Impacts, Adaptation and Vulnerability" and WGIII is "Mitigation". For myself, I have to admit I've never read II or III. One problem I know they have is that the three reports come out at much the same time, which is a problem, because logically WGII&III should be using the results of WGI. I think they fix this by getting preprints and drafts but its a teensy bit unsatisfactory. Logically, they would be staggered at approximately 2 year intervals over the approximately 6 year IPCC cycle.
ps: this blog is now proud to be a listed on Planet Fleck, a blog-aggregation service run by John Fleck. Apologies for spamming it with three posts in a row - don't worry, I'm not usually this prolific.