During question time toward the end of the recording (55min 15sec) he says:
Just a historical note, the guy who started this was a Swedish chemist whose lab I used to work at Stockholm by the name of Arrhenius. He won the Nobel Prize for chemistry and for his understanding of the temperature dependence of chemical reactions he got the Nobel Prize. He got into this and he started the whole global warming thing because he was actually trying to explain ice ages and he saw CO2 varied and temperature varied and he figured maybe CO2 caused the Ice Age. Now I don’t think anyone believes that anymore …
In other words, the whole idea that global warming is caused by CO2 came out of the need to explain what caused the Ice Age—a mystery that still eludes modern scientists.
In the Wikipedia entry on Arrhenius it says:
He was the first person to predict that emissions of carbon dioxide from the burning of fossil fuels and other combustion processes would cause global warming. Arrhenius clearly believed that a warmer world would be a positive change. From that, the hot-house theory gained more attention. Nevertheless, until about 1960, most scientists dismissed the hot-house / greenhouse effect as implausible for the cause of ice ages as Milutin Milankovitch had presented a mechanism using orbital changes of the earth (Milankovitch cycles). Nowadays, the accepted explanation is that orbital forcing sets the timing for ice ages with CO2 acting as an essential amplifying feedback.
Note the term “amplifying feedback”. This means that Milankovitch cycles are not enough to explain the Ice Ages, which is understandable considering the relatively small variations in orbital parameters for the earth. So, they added a positive feedback mechanism from CO2. A positive feedback means the system is unstable, which explains why many scientists today are concerned about global warming and the earth reaching an unstable tipping point.
The problem is that these scientists have ignored the huge climate catastrophe of Noah’s Flood. By ignoring the Flood they cannot explain the post-Flood (Pleistocene) Ice Age. The Ice Age was the earth’s thermal response to the massive climate shock caused by the biblical Flood. It was largely the volcanic activity during that year-long event that produced the necessary conditions—warm oceans and volcanic dust high in the atmosphere. But the earth returned to equilibrium in about 700 years, demonstrating that it is a stable system. The biblical Flood provides the only explanation for the Ice Age.
See how a wrong understanding of the true history of the earth leads to a misunderstanding of what is happening in the present. And a wrong understanding will lead to wrong decisions about what we need to do.