Complex sentence: He says a greenhouse effect exists, "Sunday Telegraph", 5 November 2005 and that CO 2 contributes to it, but claims there is no "causative link" from CO 2-concentration to global average temperature.
Split into simpler sentences: He says a greenhouse effect exists, "Sunday Telegraph", 5 November 2005 and that CO 2 contributes to it. He questions whether there is a "causative link" from CO 2-concentration to global average temperature.