Hacker News Reader

Comment by gd1 | Hacker News Reader

From your link: "The trigger for these mass extinctions appears to be a warming of the ocean caused by a rise of carbon dioxide levels to about 1000 parts per million."

That is fucking miles away. At the other end, C3 plant life goes extinct if CO2 falls below 250ppm or so? So why don't you alarmists get your knickers in a twist about that "tipping point"?? If we hadn't dug up and put some fossilized carbon back into the carbon cycle (where it bloody well came from in the first place) then we'd be facing that extinction scenario instead.

View on HN

There's little risk of CO2 shortage. Every animal on the planet exhales it. Burning fossil fuels was never necessary.

>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.

Reply on news.ycombinator.com