This is covered in an earlier post of his. At current growth rates, we’ll start noticeably heating the Earth in only a few hundred years. Not from the greenhouse effect, but from literally saturating the Earth’s capacity to radiate excess energy as heat into space.
This is a raw physical limitation. How we use and how we generate the energy are irrelevant details. The only thing that matters is Earth’s ambient temperature, the additional wattage being used planetwide, and the Earth’s radius. Past a certain point, Earth’s equilibrium temperature will rise well past current levels, and rapidly.
