Can Humans Affect The Earth?

Can humans have an effect on something as large as the Earth?

Just doing some ballpark calculations, if each of 200,000,000 cars in the US uses 600 gallons per year, and all the carbon in that gasoline gets converted to CO2, then that will produce 4.8 trillion kg, or 4.8e12 kg of CO2.

The total mass of the atmosphere is 5.1e18 kg. So US gasoline consumption contributes about 1 part per million per year to the to CO2 content of the atmosphere.

Doesn't seem like much, but the current concentration of CO2 in the atmosphere is 365 ppm. Most of the excess CO2 has been added over the last 60 years, and ice core data indicates that we are now at 87 ppm over the pre-industrial average of 278 ppm of CO2.

So that's a pretty good check on my calculations. If we went steadily from 0 to 1 ppm in 60 years, we should have added 30 ppm during that time. If the US consumes a third of the world's gasoline, then we'd expect an extra 90 ppm of CO2.

So if in reality there is an extra 87 ppm, and ballpark figures predict an extra 90 ppm, and the baseline was 278 ppm, then we can be pretty sure that human activities have increased atmospheric CO2 by 31%.

So, yes, human activity can have a huge impact on the Earth, big as it is.