The completely unnecessary deaths of millions starving each year or never receiving an education seem important to me as well.
The other option is here: http://m.smh.com.au/environment/climate-change/too-hot-to-live-grim-longterm-prediction-20100510-uoqw.htmlEnforcement is the threat of force. I'm not saying there aren't challenges with consequences so dire that the threat of force is an illegitimate option, but we have to be honest. The purpose of a unifying world government would be to threaten violence to make people do things against their will, and it would do that on a larger scale than has ever been seen before.
I don't disagree that there some truly frightening downsides to a single governing body(or binding agreements so strong that it may as well be a single government). I am saying that the alternative is the end of modern civilization. And once we've burned all the accessible oil there will be no restarting the industrial revolution. It'll just be the end.
I get the importance of managing climate change, really, but I'm not sure why it's a "unified world government is the only solution" situation. At least not yet. If any issues did necessitate it, the global environment and asteroid impact threat would pretty much be the ones.
If we had a system of laws that forced the government to intervene in terrible situations many of them would be fixed before they ever became an issue.
Remember all those Muslims, atheists and homosexuals that Sally Kern had killed? Me neither. Without the Feds people like her would have more power to do what they want. Her counterparts in the third world are busily committing atrocities that she only dreams about.
Even with all the bad things you can avoid, at some point, you're basically just going in with guns and telling people that they have to live a different way than they do. Now, there's lots of oppressed religions, creeds, ethnic minorities, genders, etc, that would love for someone to come into their corner of the world and make the bad people stop doing the bad things, but at that point you're basically advocating the Bush Doctrine (albeit more competently managed).

