Did you check my links? "Collapse" may have several definitions; generally for a complex society or ecosystem it's a rapid simplification, reduction of exchanges and population.
Here is our situation: as you may have heard, every year around August we reach the "Overshoot day". That means that we use more resources (even renewable ones) than the Earth can produce (its carrying capacity), i.e. we're actually "mining" renewables resources such as oceans, soil, forests, etc. That means that the quantity of renewable resources globally available tends to go down while our resource usage still goes up.
At some point, our resource usage WILL fall down UNDER the line of globally available renewable resources. The longer we wait, the LOWER we will need to back down.
Also I don't really get where you're going with your fossil fuels example. We switched from renewables to fossil fuels back in the 18 and 19th centuries because they're so much denser, easier to use and powerful than renewables. They enabled the "great acceleration" by providing almost limitless energy, and doing without them is a tremendous, unprecedented effort.
Human history is about getting better energy sources: our ancestors got bigger brains by eating meat (more energy). Then they invented fire (more energy) to make their food more digestible (more energy). Later on they invented agriculture (more energy), then burned forests for more energy, and switched to peat and coal by lack of wood (more energy), then oil and gas and nuclear (still more energy). Notice that we never "switched" from an energy source to another: we piled them up. Coal usage nowadays is higher than it ever was during the 19th and 20th centuries. See
https://jancovici.com/wp-content/uploads/2016/04/energie_gra...
For the very first time in 300 000 years, we'll have to go from a dense, easy to transport and store energy sources to more diffuse, harder to transport and store ones. We'll have to go from an incredible abundance to relative (or maybe not so relative) scarcity. It's literally an unprecedented challenge, particularly at the global scale we're talking about.
I'm also aware of overshoot day. It's not completely terrible as a metric, but it's based on shoddy data, and in the end simply shows that we are not raw material efficient enough: https://en.wikipedia.org/wiki/Earth_Overshoot_Day#Criticism
Carrying capacity only makes sense for a given technology.
> At some point, our resource usage WILL fall down UNDER the line of globally available renewable resources. The longer we wait, the LOWER we will need to back down.
That will likely take thousands of years. Just solar and batteries can go a very very very long way. Especially if we consider that it seems the human population is going to peak after every region goes through the usual development phases (education, health, more choices for women, more economic freedom).
> They enabled the "great acceleration" by providing almost limitless energy, and doing without them is a tremendous, unprecedented effort.
Yep, and now we're likely switching back. It'll not be easy, but a collapse (big reduction in population) is very unlikely.
> Notice that we never "switched" from an energy source to another: we piled them up
Yes and no. For example we stopped burning wood for energy. We stopped burning wood for potash. Coal plants reached the point that it's uneconomical to run them in developed economies.
> It's literally an unprecedented challenge, particularly at the global scale we're talking about.
Yes, agreed. But there's nothing fundamentally preventing it. Humans are pretty much known for these sudden huge Earth-wide changes. Roads, cars, planes. Churning out war stuff.
Of course the possibility that we stubbornly refuse to allocate the required resources, dig in, and make the situation a lot worse is there. But since there's at least some minimal "rationality forcing" in climate change (meaning, that the stubborn denialist ones tend to face worse problems) it's likely that eventually people will be incentivized to allocate those resources.
Here is our situation: as you may have heard, every year around August we reach the "Overshoot day". That means that we use more resources (even renewable ones) than the Earth can produce (its carrying capacity), i.e. we're actually "mining" renewables resources such as oceans, soil, forests, etc. That means that the quantity of renewable resources globally available tends to go down while our resource usage still goes up.
At some point, our resource usage WILL fall down UNDER the line of globally available renewable resources. The longer we wait, the LOWER we will need to back down.
See https://www.sustainable.soltechdesigns.com/over-carry.html for a relatively detailed explanation and real-life examples.
Also I don't really get where you're going with your fossil fuels example. We switched from renewables to fossil fuels back in the 18 and 19th centuries because they're so much denser, easier to use and powerful than renewables. They enabled the "great acceleration" by providing almost limitless energy, and doing without them is a tremendous, unprecedented effort.
Human history is about getting better energy sources: our ancestors got bigger brains by eating meat (more energy). Then they invented fire (more energy) to make their food more digestible (more energy). Later on they invented agriculture (more energy), then burned forests for more energy, and switched to peat and coal by lack of wood (more energy), then oil and gas and nuclear (still more energy). Notice that we never "switched" from an energy source to another: we piled them up. Coal usage nowadays is higher than it ever was during the 19th and 20th centuries. See https://jancovici.com/wp-content/uploads/2016/04/energie_gra...
For the very first time in 300 000 years, we'll have to go from a dense, easy to transport and store energy sources to more diffuse, harder to transport and store ones. We'll have to go from an incredible abundance to relative (or maybe not so relative) scarcity. It's literally an unprecedented challenge, particularly at the global scale we're talking about.