Co2 unproven to cause climate change

Geologist and author of 'Green Murder', Professor Ian Plimer:

"No one has ever shown that human emissions of carbon dioxide drive global warming... No one's been able to do it."

"There have been periods of 20% carbon dioxide in the atmosphere, compared with [the] 0.04% [of today]. We didn't have runaway global warming. We actually had ice ages."