We know that there are a number of homeostatic (self-regulating) processes that affect the proportion of CO2 in the atmosphere; if it wasn't homeostatic it would have drifted off to an extreme long ago. The key question is how well and how rapidly these mechanisms can respond to an increase in CO2 levels.
The homeostasis might work in a limited range under which the biological world evolved in the recent past. Exceeding that range could quickly turn to a runaway geological event of rapid climate change, a state transition in a complex and unpredictable system.
Take for example the great oxidation event happening 2.5 billion years ago. As oxygen excreting algae began to take over methane producing organisms, oxygen started to build up in the atmosphere - first slowly, as there were lots of stuff to oxidize, like methane and iron. Eventually, these naturals sinks were saturated and oxygen levels reached the critical toxic point for the other species, leading to a runaway die-off where more and more oxygen was released and methane - a strong green house gas - rapidly disappeared from the atmosphere. This shock was so massive it produced the 400 million year Huronian glaciation - a whole planet freeze unlike any since.
So I have full faith life on Earth will eventually restore the feedback loops and get the temperatures back in the sweet spot. I have less faith that this will happen soon, or that most species, humans included, can survive such a massive transition event.
> So I have full faith life on Earth will eventually restore the feedback loops and get the temperatures back in the sweet spot.
Or just broadly adapt to the new state of things, historical data suggests that atmospheric CO2 levels did reach ~1000PPM up to the Cretaceous, with complete lack of continental ice sheets and temperate forests at the poles.
The current sweet spot is a sweet spot for us and the ecosystems we grew up in as a species, it's not a life-wide sweet spot.
Yes, the comment you replied to seems to imply that the earth is an organism that seeks to maintain a particular balance. There may be homeostatic processes, but they're not part of a grand plan to preserve life on earth.
Agreed, homeostasis is something we observe in evolved organisms, not in planets whose inhabitant organisms became self aware and industrialized suddenly.
If the role is "get the carbon, that was for hundreds of millions of yeas trapped in the crust, back to the atmosphere in just a hundred or so of years and perish," yes, we’re success up to now.
A recent comment of a recent article about who's the most responsible:
"Wake up to find out that you are the eyes of the world."
edited to say:
It's interesting that on a long enough time-line, all life on earth is destined for extinction, e.g. the sun expands and vaporizes the earth. So, in the long run, our technological prowess is likely the only hope for our furry (and not so furry) friends.
I believe the "Cretaceous Greenhouse" would make quite a good movie, considering the massive inland seas that formed during the period over the continental shelf. The majority of people on Earth would have to move house to higher altitudes.
It's mind-boggling to consider that we increased the CO2 levels from 280 to 410 ppm during the industrial age. We went a quarter of the way to the Cretaceous super-greenhouse of 1000 ppm, with most of the change accumulating in recent decades. And we are accelerating.
It's hard to see how most complex ecosystems would survive that kind of change in just a century or so, evolution is simply not that rapid. Forget moving house, imagine a world where the only functional natural ecosystems are bacterial.
> I believe the "Cretaceous Greenhouse" would make quite a good movie, considering the massive inland seas that formed during the period over the continental shelf. The majority of people on Earth would have to move house to higher altitudes.
Many breadbasket lands are also fairly low-lying. The northern china plain is mostly under 50m. Even if it doesn't get covered in water, saline intrusion will seriously hurt it, as it's already starting to hurt countries with extensive coastlines and river deltas like Vietnam or Bangladesh.
I’m reading the three Wikipedia pages “Ice Age”, “Geologic Temperature Record”, and “Carbon Dioxide in Earth’s Atmosphere”. They are imo not tendentious at this time and give a fascinating introduction to the extremely complex geologic climate. For example, it’s remarked that the high temperatures in the Cretaceous were likely mostly due to the formation of Pangea and the resulting change in ocean circulation.
> I have less faith that this will happen soon, or that most species, humans included, can survive such a massive transition event.
This stuff doesn't happen in a year. And we have a bunch of ways of ego-engineering, what's missing is an acute need and the economics/political incentives, which again, an acute need would provide.
The freezing point of water creates a discontinuity in the effects of temperature change. That is, a ten degree swing that results in water freezing (or melting) for most of the year is far different than than a ten degree swing in a range far above (or below) 32 degrees.
On the other hand, a positive 10 degree global increase will include regions where water freezes regularly. This will either completely change the climate of those regions, or would mean that temperature swings in the rest of the world will increase much higher to compensate.
The big cycle is caused by the reaction of magnesium silicate with carbon dioxide. Mg silicate is the chief component of Earth's mantle. As temperature increases, silicate rocks are worn away faster by rain and wind, and absorb more CO2. This CO2 eventually sinks down into the mantle as magnesium carbonate, where it is very slowly re-released by volcanoes (the majority of Earth's carbon is in the mantle). As CO2 is sequestered, the Earth cools, and the weathering of silicate rocks slows, especially when they are covered by glaciers. Then the release of CO2 by volcanoes starts to outpace the absorption by olivine, and the atmosphere warms up again.
Eventually as the Sun gets brighter, the equilibrium amount of CO2 in the atmosphere is expected to drop below the requirements for plant life, and the Earth will die. By heating the atmosphere, we hasten the arrival of the next glacial cycle, but we are (thankfully) at low risk of starving the biosphere.
