...think of the economic stimulation! Jobs everywhere from slowly having to move people a few miles inland, an excellent opportunity to build and house a large percentage of the population in new, green houses that'll do all sorts of... green things, and a compelling event to give governments a good reason to re-do public transportation and high-speed rail lines!
There is a middle way. We'll give it a good go and try to tone down our impact on the planet, but chew on this: humans, and the mammals/birds we keep (not including fish, but dogs, cats, pet birds, cattle, horses, sheep, oxen, goats, chickens, turkeys, ducks, etc.) account for 98% of terrestrial land creatures by mass. Much of the world's land now exists solely to sustain us and our various zoological friends. Maybe... JUST MAYBE, our existence is gonna leave a mark no matter what, by our sheer numbers alone. So try as we may, it just may be too little to matter. But if that's the case, we'll be ok. I refuse to believe that what ever little bit of the climate we cause is because of what we've done since we've known enough to realize what we were doing, so it's no use getting all pissy because we've having a hard time weaning ourselves off of the things that essentially have powered humanity since we knew how to use the stuff.
Maybe there shouldn't be six billion people.
...Of course we're not going to kill anyone. Or neuter them. We just need to make less babies. I won't have a kid, for humanity. Plus, I'm American. We consume upwards of 30 times as much as some peoples around the world. Me not having a kid is gonna save humanity a lot of stuff in the long run.
You're welcome!