This has all been covered by movies - Logans Run film control population the other end of the scale is Soylent Green and even the environment covered to a degree in the Highlander sequel
Currently we need to lose an extra 100 million per year (on top of current deaths) for the world population to simply tread water.
Human based emissions are based on Humans - more humans = more emissions (a few nations doing their best efforts won't make much difference more than setting an example) that is the core thing that needs addressing - I noticed all these experts and leaders seem to willfully avoid that, industrial economies want to increase there falling predicted populations to keep the cash rolling in.
Let the population increase ad infinitum and no matter how efficient a footprint each human becomes eventually the inevitable will come to slap them in the face, even if energy was cleaned up over night transport cleaned up over night populations will be competing for resources, food, water and space
With the disunited nations of this planet I can't see this problem going away.
I am not being doom and gloom waily waily woe is me, I'll be long gone.
For those that will be still here to face these potential issues then I hope pragmatism rears it's head in the worlds leaders.
