What % of current atmospheric CO2 is from fossil fuel burning?

Question

There's currently about 780 Gt of carbon in the atmosphere. How much of that comes from fossil fuel burning?

Answer 1

I don't know but that figure would be very important to the "we gotta stop using fossil fuels to stop global warming" idea. I am curious to see the answers

Answer 2

Before the industrial revolution, co2 was about 280ppm.  Now it's 360 - 380ppm, so if you say that man added all of the additional carbon, then man has added one molecule of co2 per every million molecules of air in each of the last 100 years.

Or you can say that man added 100ppm of co2 (again assuming that all the co2 is from man and not from other sources) you can say that man added 0.001% of all co2 that's in the air.

Why worry about something so small?

Answer 3

380/280=1.36 so 36% of the co2 now in the air has arisen since 1750.

Answer 4

The isotopic ratio of C12/C13 is one indicator, but I don't have that number handy.  Here is a quick back of the envelope calculation that should give the right order of magnitude.

If the question how much CO2 remains in the atmosphere directly from fossil fuel burning, the answer is roughly half of the cumulative CO2 produced by fossil fuel burning (with about half absorbed by the oceans).  A rough integration of fig1 in

http://www.pnas.org/cgi/content/full/104...

gives total emissions of about 240 Gt, so the atmospheric content would be about 120 Gt or 15%.

If the question is one of attribution, feedbacks with the ground and ocean need to be considered.  The oceans constantly exchange CO2 with the atmosphere (and dilute the isotopic signature of fossil fuel emissions).  If the oceans absorb CO2 from fossil fuel burning and then emit an equivalent amount of CO2 from natutal sources, does the emission due to chemical equilibrium constitute a part of the fossil fuel contribution?  If so, the answer is approximately 30%.

Answer 5

From a previous answerer, I'm surprised that they had an accurate count of CO2 in 1752.  I didn't know that a) someone traveled back in time with a lab or b) that someone had the same technology back then.

It's very likely that someone just pulled a number out of thin air...

Now onto the question:

Many variables to take into account, you've got the typical fossil fuels that people first think of, gas, oil, natural gas, coal.  

While not fossilized materials co2 does come from burning combustable wood, wood byproducts, etc...  

It's also generated through the fermenation process, whether in beer, burping or flatulence.  Even breathing, about 4.5% of CO2 is exhaled with every breath we take.  (I think there is a song by the Police about that...)

Up to 40% of all the gases released into the atmosphere by a volcano is CO2.

It is theorized that five hundred million years ago carbon dioxide was 20 times more prevalent than today.

The oceans hold about 50 times more carbon than the air does, and often acts like a giant sink for CO2.

CO2 has a huge role in photosynthesis, plants take CO2 from the air and process it into Oxygen.

Is someone is to put a percentage on the current atmospheric CO2 from fossil fuel burning, they better take into account all of the CO2 producers.  And, from that, do they then take away the CO2 absorbed by all natural and man made processes?

While I think it's possible to get a really 'rough' percentage, I think it's a highly volatile value with a lot of changing values.

Answer 6

0.00000001% ...... IF you don't count Al Gore's pollution-spewing travels around the world..... making BIG $$$$.....giving speeches about how WE.....NOT HE....should be more responsible in our use of energy!!

Answer 7

it's something ridiculus like .02 %

Answer 8

According to atmospheric CO2 proxies, the concentration prior to the Industrial Revolution was ~280 ppm.

http://www.iitap.iastate.edu/gccourse/ch...

http://globalwarmingart.com/wiki/Image:C...

Now the concentration is about 384 ppm.

http://globalwarmingart.com/wiki/Image:M...

We know this increase is virtually entirely due to human emissions from fossil fuel burning from examining isotopic ratios:

http://www.realclimate.org/index.php?p=8...

Going from 280 to 384 ppm is a 37% increase.  If there are currently 780 Gt of carbon in the atmosphere, this makes 211 Gt from fossil fuel burning.