The video mentions these five things:
In the video Wrightstone mentions a statistical method that produces hockey sticks. I would have liked to see a little more detail on why that was but I know that sometimes these math topics can be quite involved.
Tree ring data growth is a bad proxy in most cases. The only cases where it is good is when the temperature is the great inhibitor of growth. Now carbon dioxide is a significant helper for plant growth in general. By using tree ring data from cool, warm or hot places; they are taking a proxy for carbon-dioxide as a proxy for temperature, and then using that to show a correlation between carbon-dioxide and temperature.
