"the only way to get population under control on Earth is to balance the number of births and the number of deaths.

There are only two ways to do thius:- have fewer babies (The modern Chinese solution), or let/cause more people to die - the historical solution."

I'm sorry, but stiffling medical advances so that you let people die and telling families not to have two children is out of the question.

"This problem is essentially solved in the first world through education of women, high quality of life, and contraception. In the third world, we face a problem that will dominate the future of the whole globe."

Just women? High quality of life and contraception are good ideas.

"The amount of fuel that must be burned to get one person into space is about the same as that person would use in a whole lifetime on Earth.

Now, if you want to get BILLIONS of people into space (and the infrastructyure that they need to survive), and you want to do it fast enough to beat population growth on Earth, then you've got to burn chemical energy tens or huindreds of times faster than the whole world is doing at the moment."

"A few tens or hundreds of space launches every year may be insignificant in their effects on the upper atmosphere, but tens to hundreds of MILLIONS of launches?"

So, are we too late as a space fairing world? Gas prices are obsurd in most areas and someone's putting the price tag. I'm not a big fan of Methane (green house gas), but in a controlled situation, by all means: http://www.habitablezone.com/nexus/index.asp?svcpt=space

For now, thank goodness for robotic missions AND don't forget that in the future, we'll need something as big of a horse as our current shuttles in order to build anything substantial.