My horizon for civilization collapse is "probably not before 2030".
The most likely scenario I perceive is heavily populated tropical and subtropical areas becoming uninhabitable, initially via failure of subsistence farming, leading to mass migration, and rise of fascistic governments in temperate regions in reaction. Fascistic governments characteristically start wars. Wars in the presence of other fascistic governments spiral out of control, ending meaningful global commerce and triggering global economic collapse. Spiraling war tends toward thermonuclear exchange.
All this happens well before, e.g., significant ice sheet collapse, or climate-caused loss of temperate-zone agriculture.
Given global economic collapse, CO2 production might fall off as extraction and delivery are disrupted, but processes already begun would take long to wind down. Thus, ocean acidification might still collapse fisheries and eliminate major protein input for whole regional populations. Fisheries anyway depend on reliable fuel delivery.
We see hints of all of the above already, with massive migrations to Europe attempted from southerly countries where climate stresses have released forces that tend to civil war; and falling fishery yield. Numerous separate phenomena all produce waves of refugees, whether water stress, declining ag yield, or even migration from immediate neighbors that exceeds already stressed local carrying capacity.
Fascistic governments are gaining in all regions; the US's step back must be counted as a blip, as very nearly half its population voted for continuation, and their elected representatives even tried to force the issue.
My question is not, how can we slow global climate disruption; it is, how can we prevent near-term global civilizational collapse? Collapse does not seem like the best way to reverse climate disruption, presuming it would even work.
If methane clathrates and permafrost carbon are released by (already well begun) local extremes of arctic warming, or loss of sea ice reduces albedo, falling industrial CO2 might not slow temperature rise or ocean acidification. Global nuclear fallout, "nuclear winter", and vaporized industrial base would make any sort of recovery difficult and slow, over decades or even centuries.
I think I agree with you on the big lines. Although I'm guessing large population migration will be more due to rising water (most humans live along some cost line). And if millions of people have to move, there will be wars with or without fascit goverments. With this scenario, the 10 year time frame seems pessimistic, I think 2050 is more likely.
Either way, the earth system will regulate, it would be nice if civilisation managed to survive the transition. I'm pretty sure there will still be humans around, happy humans I'm not so sure.
Agriculture will certainly collapse in many places long before sea level rise is noticeable.
We see reduced rainfall in many areas already, enough to have materially affected crop yields and triggered political instability, generating refugees. (Increased rainfall in other places doesn't help.) Insect populations are collapsing already. I don't think we know how low such populations may go before loss of pollination affects crop yields.
The only good news is that renewable power cost is still in free fall. It is not clear if it can be built out fast enough to cut CO2 output. Desalination will fill in for rainfall in some places, rescuing yields, although probably not in the places that will produce refugees.
It's important to remember that cutting CO2 output is simply not enough. We need to displace all fossil combustion for energy with renewables and also generate enough power to sequester the CO2 we've already released by burning fossil fuels. The magnitude of the problem cannot be overstated.
The most likely scenario I perceive is heavily populated tropical and subtropical areas becoming uninhabitable, initially via failure of subsistence farming, leading to mass migration, and rise of fascistic governments in temperate regions in reaction. Fascistic governments characteristically start wars. Wars in the presence of other fascistic governments spiral out of control, ending meaningful global commerce and triggering global economic collapse. Spiraling war tends toward thermonuclear exchange.
All this happens well before, e.g., significant ice sheet collapse, or climate-caused loss of temperate-zone agriculture.
Given global economic collapse, CO2 production might fall off as extraction and delivery are disrupted, but processes already begun would take long to wind down. Thus, ocean acidification might still collapse fisheries and eliminate major protein input for whole regional populations. Fisheries anyway depend on reliable fuel delivery.
We see hints of all of the above already, with massive migrations to Europe attempted from southerly countries where climate stresses have released forces that tend to civil war; and falling fishery yield. Numerous separate phenomena all produce waves of refugees, whether water stress, declining ag yield, or even migration from immediate neighbors that exceeds already stressed local carrying capacity.
Fascistic governments are gaining in all regions; the US's step back must be counted as a blip, as very nearly half its population voted for continuation, and their elected representatives even tried to force the issue.
My question is not, how can we slow global climate disruption; it is, how can we prevent near-term global civilizational collapse? Collapse does not seem like the best way to reverse climate disruption, presuming it would even work.
If methane clathrates and permafrost carbon are released by (already well begun) local extremes of arctic warming, or loss of sea ice reduces albedo, falling industrial CO2 might not slow temperature rise or ocean acidification. Global nuclear fallout, "nuclear winter", and vaporized industrial base would make any sort of recovery difficult and slow, over decades or even centuries.