This is an excerpt from a paper I am writing titled “The Biochemical Effects of Increased CO2 Concentrations on Human Health and on the Ecosystem Stability.” It is more explicit than the actual draft paper, and the version I’ll submit to a journal will not mention Gaia. But the essence is the same.
The present paper examined some factors not typically highlighted in the climate change mitigation discussion, such as the multiple adverse effects of current and near-future CO2 concentrations on human health [6-13]. Of these effects, the most problematic one is perhaps the “reverse Flynn effect” (“global dumbing-down”) observed in terms of a decline in human cognitive abilities during the past few years [45]. It is not certain that it can be attributed to CO2, but it is a possibility that cannot be discounted [13].
Earth’s biosphere can certainly survive at CO2 concentrations much higher than the current ones because it did during the first part of the Cenozoic [46]. In the short term, however, the survival of humans depends on their capability to cope not just with the temperature increase but with the biochemical factors involved with the increased amount of CO2 they breathe. They may succeed or not in curbing CO2 emissions and eventually reversing the trend, but it matters little to the future of the ecosystem. If they don’t succeed, they will quickly go extinct, but the ecosystem will reabsorb the emitted CO2 in times of the order of hundreds of thousands of years [47]. Then, it will return to its original compensation trajectory designed to match the solar intensity increase of the past 10-20 million years, perhaps returning to Pleistocene-like conditions. The extinction pulse created by the human perturbation may take a longer time to reverse, millions of years, but species diversity can still be recovered in a few million years [52], much shorter than the expected remaining lifespan of the biosphere of the order of one billion years [2], [3].
Then, Gaia will still have several hundred million years to continue Her great experiment with Earth’s ecosystem. The changes will be slow but enormous. Progressively lower CO2 concentrations will lead to the extinction of C3 plants, which will be replaced by C4 ones. It may spell death for the majestic forests of the Holocene, but maybe trees will learn how to pull water up from the roots even with their stomata partially closed, in C4 plants. More likely, Earth’s surface will become mainly grassland with extensive savannas, prairies, steppes, and more. The highly oxygenated atmosphere will lead to the development of new, highly complex lifeforms. Imagine something like the “Mammoth Steppe” of Pleistocene times, with even larger animals. Will Gaia also repeat the experiment with self-styled “sapiens” species? Who knows? She’ll surely be thinking about that.
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Thanks Ugo. I'm pretty interested in the rest of this year, myself, but like you, I wonder about the broader future, as well.
What about that CO2? It has a fairly narrow window of wavelengths, for which it is effective as a greenhouse-gas. Methane is complimentary with the wavelengths it effectively absorbs and reflects-back.
Gaia is emitting a lot of methane in recent decades, and not just from human activity.
Maybe Gaia is going to REALLY finish off this ice age we are in a softer version of.
https://www.youtube.com/watch?v=JCt2MhOzWVE