Why do we need CO2 to be present in the air we breathe?
We produce CO2 just fine through a process called cellular respiration.
You should do some research on the human health benefits of increased CO2.
If you're going to make a claim, how about you support it like I did?
People breathe into paper bags. Why is increasing CO2 helpful then?
Because you do need CO2 as a buffering agent. If you're panicking, it's to stop you from releasing too much CO2 and going into alkalosis. But if you always breathe into a paper bag you're going to either suffocate or suffer from acidosis.
There is such a thing as too much of something that is a good thing in some situations. You do understand that concept, right?
If you removed the CO2 from the atmosphere, you would die.
Uhh, no. You produce your own, constantly in a lot higher concentrations than what's in the atmosphere, about 100 times more.
You need to breath CO2 to survive.
Give me a citation for this. You release CO2 in your breath - you do need to do that to survive.
In some plants and fruits the nutrient values increase. The decreases seem relatively insignificant.
So says you. Citation?
Evolution takes multiple generations. You don't do it in 10 years, certainly not as human beings.
The known benefits of increased CO2 to agriculture seem to outweigh the results of that one study.
Uhh no that's not what most studies have said. Increased temperatures are bad for evaporation rates which is the largest limiter of plant growth - water.
And really water controls the CO2 content inside the leaf (which is what matters) more than the CO2 concentration in the air.
The impacts of climate change on agriculture have been forecast to be mostly negative, despite CO2 increases. This is due to the increase of weeds, extreme weather events and insects that will follow an increase in temperature and climate instability.
A few places that are very high elevation or very cold will benefit, Canada for example. Lucky me, I have family in Canada.
What is the optimal CO2 ppm for plants?
It depends on the plants. Some plants, like corn and sugarcane receive little to no benefit from increased CO2.
What was the average CO2 ppm in the atmosphere over the last several hundred million years?
Since humans have been around, it's never varied over about 250ppm. We're now at 400ppm.
source
If you go far back enough, CO2 has been higher. But it hasn't been this high since humans have existed.
