What if humans were always CO2 neutral?

[chrissreef]

Is there a website or scientific article estimating what the planet or CO2 levels would be like if humans had/have always been CO2 or pollution neutral? (recycling, organic growing, renewable resources etc.)

If the industrial revolution never occured or if it had but technologies like wind/hydro power and mass transit fully developed/integrated? How much different would medicines/medical technology be?

How close would CO2 and other pollutants be at compared to now? Would reefs, rain forests and populations of various animals be in peril at all?

(I'm going to assume planes and boats require fossil fuels)