You are quite right to point out the population and resource aspects. The world population has tripled since 1950 but these extra 5.4 billion people use up more than three times the amount of resources, far more wastefully in many cases, than was possible right after the end of WWII. Real needs, plus many less vital demands, from all these extra people have prompted much more farming, which has resulted in massive land clearance and deforestation, so that (previously) large carbon sinks around the world are now much smaller. Not the whole issue but very significant.