People who say we'd better stop breathing because of the CO2 we exhale are just demonstrating what dumb shits they are.
Fortunately saloomy didn't say that and was merely highlighting the stupidity of claiming they were going to cut all emissions, and by definition that includes CO2 emitted by breathing.
Maybe by your definition but that's taking it to a silly extreme. What they're talking about is emissions of carbon that have long been sequestered from the short term carbon cycle. If you want to be a lawyer and take it to that extreme that's your prerogative but that's obviously not what they meant.
no long term net effect on the level of CO2
If all humans started wearing masks that captured all the CO2 they breath out then yes, there would be a net effect on the level of CO2.
You don't appear to understand that net CO2 emissions include all sources of CO2, including people breathing.
The plants don't follow people around going, "here, let me have that CO2 you're breathing out", they just draw from whatever is in the atmosphere. If that came from a coal power station the plants don't go, "Sorry, wrong C02"
Sounds like you don't understand the concept of "net" very well. In order to human and other animals to exhale CO2 plants have to extract that CO2 from the atmosphere in the first place. The net effect is zero. Once it's in the atmosphere it doesn't matter where the CO2 came from. It's in the atmosphere. Breathing doesn't change the level in the atmosphere because the CO2 was already in the atmosphere a short time before. Burning fossil fuels takes carbon that has been out of circulation for hundreds of millions of years and puts it back in circulation increasing the level of CO2 in the atmosphere.
So if people started capturing the CO2 they exhale how much difference would that make? I did a little research and found that a person exhales about 2.3 pounds or 1.04 kilograms of CO2 per day. Multiplying that by 365.25 gives about 380 kilograms per year. Multiplying that by 7 billion people gives about 2.67 gigatonnes of CO2 per year exhaled by humans. Sounds like a lot but total human emissions from fossil fuel burning and other industrial processes were 35.9 gigatonnes in 2014. So capturing human human exhales would make a slight difference but it wouldn't stop the rise of CO2 in the atmosphere, just slow it down a bit. It would be much easier just to cut back on fossil fuel combustion emissions by that much.
just demonstrating what dumb shits they are