evidence: Flashback - Geologist Ian Plimer on Climate: ‘We Have Been Cooling Down for the Last 4000 Years’ PLIMER: "We have been cooling down for the last 4,000 years. So if people say, ?Oh, the planet is warming,' well, it’s all about when you start the measurements. If we look at the last 38 years, there has been no change in temperature. If we look in the last 150 years, we’ve had three warming period and three cooling periods, with a total warmth of about .6 degrees Celsius. They wonder why it warms. I mean, 1850, what happened then? Oh, yes, that was the end of the little ice age. Do you think it’s going to warm or cool after little ice age? Of course it's gonna warm. So if you start taking measurements from 1850 and the industrial revolution, we have been warming. If you take measurements from the medieval warming, we've been cooling, we cooled about five degrees since then. If you take measurements from the Roman warming, we've cooled about five degrees. So as soon as someone tells you the Earth is warming, the reply you give is, 'Since when?'"