Skeptical Science Forum

Full Rebuttal:
The very first time you learned about carbon dioxide was probably in grade school: We breathe in oxygen and breathe out carbon dioxide. Any eight-year-old can rattle off this fact.

It should come as no surprise that, when confronted with the challenge of reducing our carbon emissions from the burning of fossil fuels, some people angrily proclaim, "Why should we bother? Even breathing out creates carbon emissions!"

This statement fails to take into account the other half of the carbon cycle. As you also learned in grade school, plants are the opposite to animals in this respect: Through photosynthesis, they take in carbon dioxide and release oxygen, in a chemical equation opposite to the one above. (They also perform some respiration, because they need to eat as well, but it is outweighed by the photosynthesis.) The carbon they collect from the CO₂ in the air forms their tissues - roots, stems, leaves, and fruit.

These tissues form the base of the food chain, as they are eaten by animals, which are eaten by other animals, and so on. As humans, we are part of this food chain. All the carbon in our body comes either directly or indirectly from plants, which took it out of the air only recently.

Diagram by John Cook


2010-09-24 03:14:27	BASIC Rebuttal 129: Breathing contributes to CO2 buildup
climatesight Kate climatesight@live... 140.193.241.152	Notes: Here's a very similar, but less technical, version of the intermediate rebuttal, which I also wrote (pending here: http://www.skepticalscience.com/thread.php?t=189&r=19) Summary: By breathing out, we are simply returning to the air the same CO2 that was there to begin with. Full Rebuttal: The very first time you learned about carbon dioxide was probably in grade school: We breathe in oxygen and breathe out carbon dioxide. Any eight-year-old can rattle off this fact. It should come as no surprise that, when confronted with the challenge of reducing our carbon emissions from the burning of fossil fuels, some people angrily proclaim, "Why should we bother? Even breathing out creates carbon emissions!" This statement fails to take into account the other half of the carbon cycle. As you also learned in grade school, plants are the opposite to animals in this respect: Through photosynthesis, they take in carbon dioxide and release oxygen, in a chemical equation opposite to the one above. (They also perform some respiration, because they need to eat as well, but it is outweighed by the photosynthesis.) The carbon they collect from the CO₂ in the air forms their tissues - roots, stems, leaves, and fruit. These tissues form the base of the food chain, as they are eaten by animals, which are eaten by other animals, and so on. As humans, we are part of this food chain. All the carbon in our body comes either directly or indirectly from plants, which took it out of the air only recently. Therefore, when we breathe out, all the carbon dioxide we exhale has already been accounted for. We are simply returning to the air the same carbon that was there to begin with. Remember, it's a carbon cycle, not a straight line - and a good thing, too!
2010-09-24 09:27:23	Moved this from the Authors Forum to the Basic Rebuttal forum
John Cook john@skepticalscience... 124.185.151.34	Would it be getting too preachy to contrast CO2 exhalations with fossil fuel emissions at the end? Eg - something like "In contrast, with fossil fuel emissions, we are taking carbon out of the ground and injecting it into the atmosphere. This is causing a steep rise in atmospheric CO2 levels."
2010-09-24 10:27:56
doug_bostrom dbostrom@clearwire... 184.77.83.151	Stepping back for a moment, it's unbelievable (or ought to be) that this argument would have to be dealt with. Short, sweet treatment. I'm in rare disagreement w/JC on this; I don't think it needs any more complication. Somebody will probably gripe about "photosynthesis" having too many syllables but this gets my vote straight off.
2010-09-24 11:47:23	Rare disagreement?
John Cook john@skepticalscience... 124.185.151.34	What about the time you disagreed with the whole concept of basic rebuttals? :-) Nevertheless, thumbs up from me too.
2010-09-24 13:37:54
doug_bostrom dbostrom@clearwire... 184.77.83.151	JC: What about the time you disagreed with the whole concept of basic rebuttals? Huh. This reminds me how once, just once I tapped another car with mine, 25 years ago, and am I permitted to forget? No! "Be careful, remember that car you hit back in Pittsburgh!" Yes, dear!
2010-09-24 14:07:19	Oh oh, Doug and I are bickering like an old married couple
John Cook john@skepticalscience... 124.185.151.34	I'll have to learn to forgive and forget about the whole plain-English-gate incident :-) Kate, sorry we hijacked your thread with our personal baggage - anyone else to comment on this rebuttal, get this discussion back on track?
2010-09-24 15:38:12	Back on track
James Wight jameswight@southernphone.com... 58.105.164.221	Here's another thumb for this basic version.
2010-09-24 20:27:49
Riccardo riccardoreitano@tiscali... 192.84.150.209	4th thumb :)
2010-09-24 22:33:48
Paul D chillcast@googlemail... 82.18.130.183	Well if you are going to tackle all the crazy ideas out there, you may as well cover this one as well as the more complex ones! I think the statement 'By breathing out, we are simply returning to the air the same CO2 that was there to begin with' is usually made by those that know very well it is a load of rubbish, or just like winding people up. I think the rebuttal is for those that haven't a clue and might agree with it because of a lack of good education. I like the nice clear language. Well done Kate.
2010-09-25 02:22:31	OK
nealjking nealjking@gmail... 195.202.153.35	good to go
2010-09-28 07:29:10
climatesight Kate climatesight@live... 74.216.127.59	Sounds great! Thanks, everyone! Kate