Dynamical systems are often sensitive to the value of a parameter, its rate of change and/or its rate of rate of change.

Eg. You can warm milk to a certain temperature (the parameter) on a stove on gentle heat and it will be fine. If you warm it to the same temperature on high heat (i.e. increased rate of parameter), it will burn. That's because the convection process in this system has limited maximum speed.

If you look at when previously the Earth's atmosphere had high CO2, it took hundreds of thousands to many millions of years get there. We did it in a 100 years, so at least a thousand times faster.