The Collapse of AMOC is just one working ecological system that can quickly break down due to consequences of too much heat in the atmosphere and sea. We can relate to it because the Gulf Stream has been anomalously heating Northern Europe, where many of its populous cities are above the latitude of Montreal. Without the stream's movement, we can expect more effects, such as the decline in fish stocks, changes in hurricane development, sea level changes independent of the addition of melting land ice's fresh water.
Other predictable systems such as reliable monsoons, permafrost, and glaciation: changes in these can stress the natural world that needs to be predictable for us to exploit it in our current cultures. When to plant and what to plant? Will the birds and insects return to pollinate? Will the forests be there to stabilize the soil?
A trigger point is where the process is unbalanced just enough to be a self-sustaining cascade, usually exponential in nature. A bit of the energy released contributes to the energy that is doing the releasing. Humans, who are fairly innumerate to begin with, have a hard time understanding processes with exponential velocities. When we drop rocks off a cliff, that's 32 feet per second squared, but we're rarely high enough or in a place to observe its motion over a period of more than a few seconds. It's just not in our experience.
The feedback loops we have here not only feed the process releasing the energy, but any other nearby process that by itself would take more energy to reach that tipping point. They are not isolated.
The amount of CO2 in the air already is a huge ecological debt. This is the debt that matters. Innumeracy is keeping decision makers from measuring the cost of shutdowns, conversions and climate refugee migration against the cost of the shutdown of natural processes that were assumed to be free throughout the development of human cultures. Cultures that value property rights - the climate does not value property rights. Cultures that rely on natural growth cycles, natural animal migrations, tide heights, snowpack growth and melting - these cycles will change. Cultures relying on the effect of polar ice on sea salinity and the jet stream - we can't change these but the climate can.
We have to start by not increasing the debt. For things we directly control, that means literally not burning carbon emitters to run machinery, or as a source of heat, not removing carbon sinks like forests and oceans. The trouble there is that forests are worse carbon sinks the hotter it gets, and the oceans already have absorbed much of the new CO2 and can't keep up.
You can watch the interplay of source and sink in the measurements of Co2 from Mauna Loa (and Maunakea while Mauna Loa is erupting). When the global north, which has the most forestry, is growing, the amount of CO2 goes down. When it's more idle, the amount goes back up. But the net addition of carbon outside this cycle pushes the next peak higher than the year before.
[ https://gml.noaa.gov/ccgg/trends/ ]
But it does prove that there is a natural process that takes carbon out of the air. As long as those plants don't burn, that carbon can be added to the soil. Can a similar process be optimized and scaled? Can the process that does it actually be carbon neutral or negative? Unfortunately, it's a tech fix, which means it won't happen unless someone makes money.
