This whole assessment is based on a very problematic premise: that the underlying preconditions for human population will remain basically constant--i.e. availabilty of ample food and water, liveable climate range, etc. Current chaotic swings in temperature (heat waves, floods, and freezes worldwide) make me doubtful that any of these assumptions will still hold true. Like every other creature, humans depend on a stable, reliable climate to survive. There is no guarantee at all that our global agricultural infrastructures will be able to wiithstand the accelerating pace of climate destabilization due to CO2 emissions. Our population may undergo a massive die-off long before 2100--or even 2050--if global heating and chilling from alternating heat domes and polar vortices wipe out our croplands and other ecosystems that we depend on.