The response time of the troposphere is relatively short, from days to weeks, whereas
the stratosphere reaches equilibrium on a time scale of typically a few months.
The first rate seems to be far slower because there are no winds in the
stratosphere so that
equilibrium can only be
reached by diffusion of heat which is really slow; on the other hand we are pumpimg around 1.5 ppm of CO2 into the troposphere every year, over a base value of around 380 ppm.