Reminder: If CO2 levels fall below 150 ppm there will be a mass extinction of land-based plants.
It is a grave mistake to believe that CO2 as such is bad and must be removed from the atmosphere. It is an essential fertilizer for both phytoplankton and land-based plants (at current levels these plants are in effect starved for CO2, because they evolved during geological time periods with much higher CO2 levels).
I hope this is not your usual standard of thinking or argument.
At what CO2 level in the atmosphere would land-based vegetation go extinct? should one take this into account when designing or advocating massive mechanisms to remove CO2 from the atmosphere? once you've admitted that some CO2 level is good for the planet, why and how do you determine an ideal/target level?
Your asserted number (1,100 GtC) seems to be a wild exaggeration: "In the period 1751 to 1900, about 12 GtC were released as CO2 to the atmosphere from burning of fossil fuels, whereas from 1901 to 2013 the figure was about 380 GtC." [1]
"From 1870 to 2014, cumulative carbon emissions totaled about 545 GtC. Emissions were partitioned among the atmosphere (approx. 230 GtC or 42%), ocean (approx. 155 GtC or 28%) and the land (approx. 160 GtC or 29%)." [2] (And 230 GtC is 843 GtCO2, so that doesn't match either.)
Your asserted number appears closer to an estimate of total GtC in the atmosphere, not merely the modern addition via human CO2 emissions. Where did that 1,100 number come from?
I tracked down one scientific paper that mentions "1,100 Gt CO2" but the context is completely different from what was being claimed (total human emissions so far): it's an estimate of the remaining global carbon budget from 2011 onwards for the political goal of limiting global temperature rise to 2 ̊C.
"A temperature rise of 2 ̊C is consistent with combustion and release of around 1 trillion tonnes of carbon (1000 Gt C). The 2013 IPCC Working Group 1 report calculates the remaining global carbon budget from 2011 onwards consistent with the political goal of limiting global temperature rise to less than 2 ̊C to be 300 Gt C, equivalent to emission of 1100 Gt CO2. Current known and exploitable fossil fuel reserves are equivalent to 3100 Gt CO2, three times greater than this cumulative emissions budget. A conservative estimate of the additional fossil carbon resource that could be extracted is 30-50 times greater (~45000 Gt CO2)." [1]
Their reference for that amount is "IPCC. Fifth Assessment Report Summary for Policymakers, Working Group 1: the physical science basis (2013)". [2] However when I read and search that document that particular number is absent. A search of the full 1,552 page report [3] also comes up empty.
[1] Scott. V., Haszeldine, R.S.H., Tett, S.F.B., Oschlies, A., Fossil fuels in a trillion tonne world, Nature Climate Change 5, 419–423, 2015. (https://www.nature.com/articles/nclimate2578)
> these plants are in effect starved for CO2, because they evolved during time periods with much higher CO2 levels
Oh, the old argument trotted out again. What do you mean, plants "evolved" in the past and then what? Stopped evolving?
If plants were starved of CO2 now they would go extinct, which they aren't. To prove my point, I present exhibit A: The Amazon rainforest.
Starvation is not equivalent to death, it means that plants are not growing as fast nor as well as they would with higher levels of CO2.
This is a proven fact and has been amply demonstrated in scientific experiments; it is related to well-understood biological processes in photosynthesis. It is the reason greenhouses deliberately increase CO2 ppm. [1] And yes, the plant kingdom has evolved just a few pathways for photosynthesis that worked well at much higher CO2 levels (10-15x current) when they originated; and these pathways are not magically "evolving" to function with diminishing CO2 levels, they've merely become suboptimal given the atmospheric conditions in the last million years, and would stop working below specific levels.
Your ignorant dismissals are moronic denials of facts and science. Surely you don't pretend that there is no lower limit to the viable amount of CO2 in the air for Earth vegetation to survive?
this is why I have been trying to promote CO2 production to a target level of 1200PPM. With enough solar, biofuels and wind -- which are all net negative entry input vs energy output (which promotes CO2 production) I was hoping we could do this.
It is a grave mistake to believe that CO2 as such is bad and must be removed from the atmosphere. It is an essential fertilizer for both phytoplankton and land-based plants (at current levels these plants are in effect starved for CO2, because they evolved during geological time periods with much higher CO2 levels).