MattStat
As the Chief wisely suggests, the end of WWII is a good starting point as far as human CO2 emissions are concerned.
That is when human CO2 emissions really began to rise. [According to CDIAC the cumulated CO2 emissions over the three decades after 1945 were over two and a half times those for the three decades prior to 1945.]
As far as global warming is concerned, there is a problem, however.
The 30 years prior to 1945 showed warming, which is statistically indistinguishable from the most recent 30-year warming cycle starting in 1975 (the IPCC AR4 poster period).
Yet the following 30 years starting in 1945 showed slight cooling with two and a half times as much CO2 emitted.
There are rationalizations for all this out there, but these sound pretty hollow.
The fact of the matter is that there is no real correlation between human CO2 emissions and global temperature.
Max