No one knows what Earth's optimal level of CO2 or temperature would be because we only live in a single frame of the longest movie ever made. We can not scientifically derive the optimum without being in a different time. We can say when CO2 becomes toxic and that is at 0.6% or 16 times what it is today the highest levels 14X what it is today and animals still did fine as far as we can tell.
Farmers use greenhouses to raise their CO2 for a more optimal level for plant growth. Many believe we are deficient on CO2, global alarmist don't agree.
we do know that man contributes about 3.4% of the total CO2. If we continued on our present course we can never get to a toxic.
As you can see in this chart I personally think we are deficient on CO2:
So am I reading this right?
Does that graph show that CO2 concentrations have
been on the decline for the last 175 million years?
Is the blue line ‘temperature’?
(if yes, then what is(are) the ‘red’ line(s)?)