I agree with the analysis. The only thing I'd add (that they don't mention) is that the Earth's temperature will fluctuate wildly on it's own regardless of our CO2 output. We know this. The Earth dropped into an Ice Age and then got hot enough to thaw that ice age out all before we were even here. So the issue really has to do with finding ways to manipulate the Earth's temperature both ways, not just cool it down.