>There's little risk of CO2 shortage. Every animal on the planet exhales it.
Erm no. Exhaling it is just part of the carbon cycle, it doesn't make the net level in circulation go up or down, it isn't a sink or a source... the carbon you breathe out doesn't get magicked out of thin air. It comes from the sugars, fats and protein you eat which is then burnt by your body for energy, exhaled, photosynthesized by plants, consumed by animals, and moves on up the food chain where you eat it and we start again. Round and round. That's why they call it a cycle.
Without our intervention the net amount of carbon in the cycle would continue to fall due to weathering of rocks and sequestration beneath the Earth, eventually leading to the extinction of all trees and most (non C4) plant life. Luckily, we're digging it up to restore the carbon cycle to its former glory. I think about 800ppm should be our target.
Producing CO2 is an exothermic process, and therefore easy - just set stuff on fire and it keeps going on its own. Removing CO2 is an endothermic ("energy-intensive") process, and therefore hard; moreover, a lot of our energy-making just makes more CO2, thereby stumping any CO2 removal attempt.
In other words, low CO2 is uphill from where we are, whereas high CO2 is downhill. And the slope is steep due to the laws of thermodynamics and chemistry.
Erm no. Exhaling it is just part of the carbon cycle, it doesn't make the net level in circulation go up or down, it isn't a sink or a source... the carbon you breathe out doesn't get magicked out of thin air. It comes from the sugars, fats and protein you eat which is then burnt by your body for energy, exhaled, photosynthesized by plants, consumed by animals, and moves on up the food chain where you eat it and we start again. Round and round. That's why they call it a cycle.
Without our intervention the net amount of carbon in the cycle would continue to fall due to weathering of rocks and sequestration beneath the Earth, eventually leading to the extinction of all trees and most (non C4) plant life. Luckily, we're digging it up to restore the carbon cycle to its former glory. I think about 800ppm should be our target.