I spent about 20 minutes looking for that reference. I'm sure an actual climate scientist could provide you with a better reference.
Page 450 has a table. Historic CO2 concentration: 280ppm, "current" concentration 341ppm: a 21% increase. From that and the 60 * 10^15 moles C in the atmosphere in 1982 we can deduce around 50 * 10^15 moles C in 1800 in the atmosphere. That seems to be in the right ballpark of 14 * 10^15 moles of emissions from fossil fuels: not all of the carbon ends up in the atmosphere, e.g. some is dissolved in the ocean. Certainly the difference is not large enough (and doesn't have the right sign!) to support the theory that man made carbon dioxide didn't contribute the majority of the extra carbon in the atmosphere.
Page 450 has a table. Historic CO2 concentration: 280ppm, "current" concentration 341ppm: a 21% increase. From that and the 60 * 10^15 moles C in the atmosphere in 1982 we can deduce around 50 * 10^15 moles C in 1800 in the atmosphere. That seems to be in the right ballpark of 14 * 10^15 moles of emissions from fossil fuels: not all of the carbon ends up in the atmosphere, e.g. some is dissolved in the ocean. Certainly the difference is not large enough (and doesn't have the right sign!) to support the theory that man made carbon dioxide didn't contribute the majority of the extra carbon in the atmosphere.