<p>The answer is <em>The Carbon Cycle</em>, which includes carbon cycling between atmosphere and oceans, vegetation and soils ensure the Earth does not run out. Volcanoes add very little in proportion to Plant Respiration or Soil Decomposition or Ocean Loss (or even fossil fuel burning) - but unlike those, volcanic CO<sub>2</sub> (and similarly, fossil fuel CO<sub>2</sub>) is not accompanied by processes like Photosynthesis, Litterfall or Ocean Uptake that draw CO<sub>2</sub> out of the atmosphere. However there is some ongoing loss of carbon to Burial to Sediments.</p>
<p>Without the fossil fuel burning the fluxes (flows) were close to being in equilibrium, without ongoing consumption and enduring loss of atmospheric CO<sub>2</sub> -<br />
<a href="https://i.sstatic.net/xnn6y.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/xnn6y.jpg" alt="Global Carbon Cycle" /></a></p>

CC BY-SA 4.0
2021-07-26T07:20:09.897Z
Hi thanks for the answer, I'm not sure that it doesn't show that over millions of years without human action the carbon isn't all eventually trapped in the earths crust?
dibs487
CC BY-SA 4.0
2021-07-28T01:03:47.927Z
The diagram doesn't show everything - it is the "fast" carbon cycle, where most of the action is. The slow or long carbon cycle involves slower cycling in both directions between atmosphere and oceans and Earth' crust but the total flows are much smaller than the fast carbon cycle above - 10 to 100 million metric tons of carbon per year versus flows hundreds to thousands times greater than that. More info here -  https://earthobservatory.nasa.gov/features/CarbonCycle/page2.php
Ken Fabian
CC BY-SA 4.0
2021-07-28T06:35:04.620Z
Great, thanks the slow carbon cycle is the answer I was looking for.  I was happy with the everyday carbon cycle but didn't understand how once carbon was locked in limestone it ever returned. Would you mind editing your answer to be more specifically about the slow carbon cycle?
dibs487
CC BY-SA 4.0
2021-07-28T14:09:37.407Z
animals can also produce carbon dioxide apart from humans mining it from the crust, if you leave out mining you get biological inhaling and exhaling, which will keep the carbon cycle alive.
Tardy
CC BY-SA 4.0
2021-07-23T23:41:56.270Z
2021-07-24T06:40:35.853Z
2021-07-24T06:40:35.853Z
Ken Fabian
<p>One of my friends told me quite seriously that Gaia had evolved humans to burn the fossil fuels and thus stop the earth running out of CO<sub>2</sub>.</p>
<p>Leaving aside the obvious nonsense it did raise an interesting question, what stops us running out of CO<sub>2</sub>?  Apart from volcanism are there any processes that return carbon captured in fossil fuels and limestone to the atmosphere? Is it plausible that the planet could run so low on atmospheric carbon that plants couldn't photosynthesize?</p>

CC BY-SA 4.0
2021-08-09T11:35:09.207Z
Comments are not for extended discussion; this conversation has been [moved to chat](https://chat.stackexchange.com/rooms/128379/discussion-on-question-by-dibs487-when-would-the-earth-run-out-of-carbon-dioxide).
gerrit
<atmosphere><co2><carbon-cycle>
When would the earth run out of carbon dioxide without man made climate change?
dibs487
# When would the earth run out of carbon dioxide without man made climate change?

(Asked by: username_0 on 2021-07-23)

One of my friends told me quite seriously that Gaia had evolved humans to burn the fossil fuels and thus stop the earth running out of CO2.

Leaving aside the obvious nonsense it did raise an interesting question, what stops us running out of CO2? Apart from volcanism are there any processes that return carbon captured in fossil fuels and limestone to the atmosphere? Is it plausible that the planet could run so low on atmospheric carbon that plants couldn't photosynthesize?

**Tags:** atmosphere, co2, carbon-cycle

> **Comments:**
> **username_1**: Comments are not for extended discussion; this conversation has been [moved to chat](https://chat.stackexchange.com/rooms/128379/discussion-on-question-by-username_0-when-would-the-earth-run-out-of-carbon-dioxide).  

---

## 1 answers

### Answer by username_2 on 2021-07-23. Score: 3

The answer is *The Carbon Cycle*, which includes carbon cycling between atmosphere and oceans, vegetation and soils ensure the Earth does not run out. Volcanoes add very little in proportion to Plant Respiration or Soil Decomposition or Ocean Loss (or even fossil fuel burning) - but unlike those, volcanic CO2 (and similarly, fossil fuel CO2) is not accompanied by processes like Photosynthesis, Litterfall or Ocean Uptake that draw CO2 out of the atmosphere. However there is some ongoing loss of carbon to Burial to Sediments.

Without the fossil fuel burning the fluxes (flows) were close to being in equilibrium, without ongoing consumption and enduring loss of atmospheric CO2 -  
[![Global Carbon Cycle](https://i.sstatic.net/xnn6y.jpg)](https://i.sstatic.net/xnn6y.jpg)

> **Comments:**
> **username_0**: Hi thanks for the answer, I'm not sure that it doesn't show that over millions of years without human action the carbon isn't all eventually trapped in the earths crust?  
> **username_2**: The diagram doesn't show everything - it is the "fast" carbon cycle, where most of the action is. The slow or long carbon cycle involves slower cycling in both directions between atmosphere and oceans and Earth' crust but the total flows are much smaller than the fast carbon cycle above - 10 to 100 million metric tons of carbon per year versus flows hundreds to thousands times greater than that. More info here -  https://earthobservatory.nasa.gov/features/CarbonCycle/page2.php  
> **username_0**: Great, thanks the slow carbon cycle is the answer I was looking for.  I was happy with the everyday carbon cycle but didn't understand how once carbon was locked in limestone it ever returned. Would you mind editing your answer to be more specifically about the slow carbon cycle?  
> **username_3**: animals can also produce carbon dioxide apart from humans mining it from the crust, if you leave out mining you get biological inhaling and exhaling, which will keep the carbon cycle alive.  

---

