The next century will pass, a couple of generations will be added and subtracted and our collective actions and inactions will have taken us to a better or worse place, inevitably more sustainable. If it's a worse place we'll regret that this generation squandered the opportunity to have made it better.
At this end of that century we as individuals will have choosen to be part of the problem or part of the solution, with some self satisfaction in that choice but it's collective action one way or the other that will have been our answer to this collective problem.
Like today that place will be organized by hemispheres, continents and countries each with its own story and situation. The problem and solutions will have been divided up among those entities and there will be some sense of winners and losers in the results. That will determine the stability of society then with either wars or peace and population adjustments the most significant results.
Climate scientists realize that choices yet unmade will determine what that place will be like, so they've sorted the infinite possibilities down to a more manageable set of four general scenarios as a guide. Those are packaged as Representative Carbon Pathways for now to 2100, each with an Extended Carbon Pathway with appropriately less certainty beyond.
While the formulation of these RCPs and ECPs is very complex their purpose is to simplify the very complex task of modeling future global warming consequences. Below is a representative output.
As you can see there are four RCP/ECPs modeled. 2.6, 4.5, 6, and 8.5. Based on a large number of variables and assumptions behind each, these graphs show by year the annual carbon dioxide emissions in gigatons of CO2 into the atmosphere and the "radiative forcing", in other words what the energy imbalance is, based on the accumulation of greenhouse gases in the atmosphere. Where the curves depart is now with the actuals to date before and the predictions after. What the curve on the left depicts is when the peak of emissions occurs, and how large it is, which is a function of the fossil fuels burned vs left in the ground. An assumption for 8.5 is that around 2200 fossil fuels run out and mitigation by then is forced by availability.
The temperature difference between the last ice age and our current warm period, which carried humankind into civilization over the past 10,000 years, is less than 5°C. This is about the amount of warming that we will have caused by the end of the century if we continue as we have done in the past. Only we are doing it about one hundred times faster than nature did while trying to keep a highly efficient global economic network running.
These are all calculations built on sets of assumptions of what we might do. Like the University of Chicago modeling program on the previous page. Interesting to scientists but not what we will sense. What we will sense are the changes in precipitation, sea level and acidity, and increase in violent weather that will render our infrastructure to some degree not adapted to the environment that we will have created. The higher that these curves get up the X axis the more we will be forced to spend on adaptation and recovery. Getting to the most affordable scenario for adaptation and recovery requires early mitigation. The proverbial rock and hard place.
Like all science this is humanity's most expert interpretation of what evidence from reality says about reality. It's unequivocal as far as it goes. People are free to opine other realities but this is the one that will report for duty over the next few generations. If you would fly in an airplane built on opinions rather than science than maybe you will go for fewer facts and more wishes.
As for me, no thank you.
"Choices" outlines some of the alternatives that we can decide among.