Also if significant funding and attention was given to this problem, and people realized that the existence of life on Earth depended on it, I'm sure there'd be

Also if significant funding and attention was given to this problem, and people realized that the existence of life on Earth depended on it, I'm sure there'd be a lot of innovation, resulting in all sorts of other ideas and technologies that we haven't thought of yet. Did you just wake up for a coma or something? Recent history has shown that when faced with a life-threatening disaster, half of this country is going to deny that there's a threat at all and an expensive project to ward off a threat that's decades away won't get funded until it's too late.