2006: When they knew Earth's climate was once tropical

I have been fascinated and surprised by the idea the Earth's climate has been through so many drastic changes. In 2006 several big news companies wrote stories about the discovery, via core sampling, that the Earth's climate had once been entirely tropical. Here is one article from the 2006 New York Times. I am very interested in the ideas about earths history. I will be doing more research.

Thanks to this guy (Andrew Revkin):

https://plus.google.com/+AndrewRevkin/posts

For his study of the arctic and his 2006 article in the NY Times.