Prof. Ian Plimer: CO2 Levels Were Much Higher in the Past, and We're Dangerously Low Now

Australian geologist, Professor Ian Plimer: "CO2 in the past has been much, much higher than now. We're currently at 0.04%. For most of geological time, it was about 20%."

"And during that geological time when we had high carbon dioxide, we had three of the six great ice ages. So clearly carbon dioxide wasn't driving runaway global warming."

"We are actually dangerously low. And if we continue to follow that long-term geological trend, we will find that plants will die... We are currently at just over 0.04% carbon dioxide. That's not enough for plants to thrive. They like about two or three times that amount."