Mostly, the RealClimate blog deals with issues around modern AGW but this post
http://www.realclimate.org/index.php/archives/2008/01/the-debate-is-just-beginning-on-the-cretaceous/langswitch_lang/in
concerns the apparent fact that
"...that there appears to have been a 200,000 year period right smack in the middle of one of the warmest periods of the past half billion years, when there were ice sheets (presumably in Antarctica) that were up to 60% the volume of today's Antarctic ice sheets. How in the world do you get such large ice sheets in a high CO2 climate warm enough for crocodiles to survive in the Arctic at the other side of the planet? And this apparent glaciation is not the result of a global cold snap. As in the Eocene results quoted earlier, the tropical ocean surface temperatures are again on the order of 35C - courtesy once more of the wondrous Tex86 proxy."