Fact 1: If all the oil consumed were combusted, the resulting water would raise the sea level about 1 mm.
Fact 2: In burning oil, approximately 3/10,000th of the oxygen in Earth's atmosphere has been consumed. That's around 75ppm. This number was found from the number of barrels of oil consumed. We have seen the C02 ppm increase by about 100 since 1970 (about 15% of oil consumption occurred before 1970).
Corollary: Neither of these statistics account for a significant portion of either the increasing CO2 in the atmosphere or the rising sea level.
Corollary: based on the measured increase in CO2 and the calculated decrease in oxygen due to combustion of oil, 32% of the Co2 increase can be attributed to burning oil (not including coal).
Basically, these serve as a reminder of just how big the Earth is, but also that the increase in C02 in the air is very likely due to the consumption of oil and coal.
I made a large number of simplifications. I assure you that the general idea is right; the fact that the theoretical value was near the measured value suggests that. Just don't believe this fully; it should just give you an approximate range for the actual values.
(I had to do the math on my own. It was a combination of aspects of calculus, statistics, and chemistry. Feel free to check it for me. I often made simplifying estimates, like the oil consumed in the past 10 years and the oil consumed before 1970.)
We have consumed around 1.1 trillion barrels of oil since 1900.
By mass, around 1/7 of oil is hydrogen. This neglects alcohols and double bonds. For methane, it's 1/4 (methane has the most hydrogen by mass of all hydrocarbons)
What's in a barrel of oil?