Just because you can make a simplification doesn't mean you have achieved understanding. That understanding might be correct, or it might not. Even if you think you know the error bars are small, that doesn't mean that they are.
Given that the earth has had temperature excursions of +4C and -4C in the past 100k years it seems that there are some kind of forces that keep the temperature within that range. What are they? Climatologists are saying "tipping points" and whatnot, but if you believe the very long climate history as measured by proxies you would have to admit that there certainly SEEMS to be something that stops the temperature from rising further, and something that stops it from falling further. What are those mechanisms?
That's what a planetary climate is: an energy equilibrium. But if a forcing or feedback changes, the equilibrium will change.
The history of Earth's climate shows the limits of these changes, but that doesn't mean there are guard rails keeping us safe. It's just a reflection of the physical limits of the forcings and feedbacks. Our orbit only varies so much. Our axial tilt only wobbles so much. The sun's output only varies so much. The atmosphere can only hold so much water vapor at a given temperature. Etc.
If the sun suddenly doubled in brightness, I doubt you would expect the climate to still stay within that +/- 4C range, right? Well, atmospheric gases are also a forcing, one that we know we're changing. Granted--not at that level, but change is change. Models help us think about the sensitivity to that change, but the equilibrium must shift, somehow.
Anyway, the Earth's climate could stay well within that +/- 4C range, and the warming would still cause mankind a ton of trouble if it happens too fast. Remember that these are global average energy levels...it doesn't take much to raise sea level a troublesome amount, for example, especially since societies have built right at the water line all over the world.
Given that the earth has had temperature excursions of +4C and -4C in the past 100k years it seems that there are some kind of forces that keep the temperature within that range. What are they? Climatologists are saying "tipping points" and whatnot, but if you believe the very long climate history as measured by proxies you would have to admit that there certainly SEEMS to be something that stops the temperature from rising further, and something that stops it from falling further. What are those mechanisms?