[defrost]

  While there is a "CO2 fertilization effect" where rising atmospheric carbon dioxide can initially boost plant growth, scientists are increasingly stating that this effect is reaching its limit, meaning plants can no longer absorb as much CO2 due to factors like nutrient limitations and other environmental constraints, effectively capping the potential for further carbon uptake from the atmosphere. 

It rose in the 30 years prior to your 2016 article, it's peaked and it is unlikely there will be any further benefical effects of "greening" (not the same as "nutritional") vegetation .. and this is outweighed by the downsides of increased insulation in the atmosphere trapping more of the daily solar influx energy at the land, sea, air interface.

[ETH_start]

It would be quite odd if the CO2 fertilization effect has already peaked, given that geological history shows periods with much higher CO2 concentrations, during which plant growth was significantly greater.

In the long run, humans cannot indefinitely alter atmospheric composition without risking conditions that could undermine life’s prosperity. At sufficiently high concentrations, CO2 also impairs human cognition, as our physiology is not adapted to the extreme levels that were once common in Earth’s distant past.

That said, we should remain open to the possibility that CO2 emissions have net positive effects in the short to medium term. If that is the case, CO2 mitigation strategies could be adjusted accordingly—focusing on economically efficient transitions rather than rushing to eliminate CO2 emissions at all costs. This would mean prioritizing the replacement of CO2-emitting energy sources where it is already cost-effective, while investing in R&D to lower transition costs in areas where immediate replacement would be prohibitively expensive.

[cogman10]

> It would be quite odd if the CO2 fertilization effect has already peaked, given that geological history shows periods with much higher CO2 concentrations, during which plant growth was significantly greater.

The species of plants were at a different evolutionary stage. Further, a lot of bio matter wasn't in the form of human consumables. Algae was by and large the main CO2 absorber of prehistoric periods.

It took millions of years of growth for plants to sequester the carbon we are currently emitting. That's millions of years of adaptation to the ever changing atmosphere composition.

[ETH_start]

ChatGPT:

The optimal CO₂ concentration for plant growth in greenhouse farms typically ranges between 800 and 1,200 ppm (parts per million). Some high-intensity commercial greenhouses may use levels up to 1,500 ppm, but beyond that, the benefits diminish, and excessive CO₂ can start to have negative effects.

The current atmospheric CO₂ level is approximately 420–425 ppm as of 2024, which is significantly lower than the optimal greenhouse levels for plant growth but much higher than pre-industrial levels (~280 ppm).

--

Worth noting that at 1,000 ppm, CO2 begins to impair human cognition, and if we really want to be safe, we really shouldn't allow it to even get close to that, e.g. 700 ppm is probably already cutting it too close.

[cogman10]

Here's what a university has to say on the matter [1]

The gist of it, CO2 supplementation can be beneficial to some plants (not all plants) IFF you also tweak all other inputs into growth. Not something that happens outside of a greenhouse.

> Plants may not show a positive response to supplemental CO2 because of other limiting factors such as nutrients, water and light. All factors need to be at optimum levels.

[1] https://extension.okstate.edu/fact-sheets/greenhouse-carbon-...

[ETH_start]

Well, plant growth on Earth massively increased in the 30 years up to the 2016 study. It would be quite the coincidence that it stopped right after that study.

[nopelynopington]

> At sufficiently high concentrations, CO2 also impairs human cognition

Any time I watch the news I feel like this is already happening.