Complex sentence: Delingpole is widely known as a sceptic about global warming; he says he does not dispute that global warming has occurred, but doubts the extent to which it is man-made ("anthropogenic") or catastrophic.
Split into simpler sentences: Delingpole is widely known as a sceptic about global warming. He says he does not dispute that global warming has occurred, but doubts the extent to which it is man-made ("anthropogenic") or catastrophic.