The difference between the climate changes that happened in prehistoric times and the climate change that is happening now is that the changes in prehistoric times happened over thousands of years, and the changes we are seeing now are happening in less than a century.
He wasn't talking about prehistoric times. The Medieval Warming Period was only a thousand years ago. The glaciers in Greenland virtually disappeared, the Vikings colonized it, and there was plenty of grassland for their animals. In Britain, they were growing excellent grapes, and they were exporting wine to France! Couple of hundred years later, there was the Little Ice Age. The glaciers in Greenland, grew quickly, and pushed the Vikings into the sea, and the grape crop in Britain, ceased
to exist, as the Thames river froze solid.
There wasn't any burning of oil in either case, that caused those recent climate changes. The Earth's climate changes all the time, and mankind has nothing to say about it. Historically, the Medieval Warming Period is referred to as the Medieval Climate Optimum, because it was so favorable to mankind. And back then, only a thousand years ago, the average temperature was higher than it is now, and even higher than it will be in a hundred years from now, in the bogus computer models, that so called "scientists" are trying to palm off on us.
The Global Warming, Climate Change, has been a scam from the beginning. Just another socialist money grab, to redistribute wealth from the First World, to the Turd World.