All are good. I really enjoyed these authors when I was 7-8. I really balled my head off during some scenes in these books so be prepared. ( When Cafall was killed, I was totally wiped out. )

http://en.wikipedia.org/wiki/The_Dark_Is_Rising_Sequence

http://en.wikipedia.org/wiki/Madeleine_L'Engle

http://en.wikipedia.org/wiki/The_Chronicles_of_Narnia

More mature themes - 9+

http://en.wikipedia.org/wiki/J._R._R._Tolkien

http://en.wikipedia.org/wiki/Podkayne_of_Mars

http://en.wikipedia.org/wiki/The_Mote_in_God%27s_Eye

http://en.wikipedia.org/wiki/Paradise_Lost

You will want to have access to an OED or Wikipedia or an annotation when doing Paradise Lost.

There are some very good adaptions of JRRT to audio books. The BBC has an EXCELLENT adaptation that makes for great listening.

Brian Fagan has some very good works on history and its interelationship with climate. I attended a lecture of his when I was 12.

http://www.brianfagan.com/

The Cosmos series by Carl Sagan is available from Netflicks or you can DVR it. It touches on a number of subjects.