# Why does the emission of aircrafts at higher altitudes have a greater effect on the climate?

I am trying to understand the footprint of a flight. First Wikipedia says (without quoting a source):

The level and effects of CO2 emissions are currently believed to be broadly the same regardless of altitude.

But then there are numerous references to radiative forcing, which is supposedly almost doubling the effects of the emissions (at this point only co2, or also NOx and others?). These are never explained (it says "see below" once, but there follows no explanation below.

The article on radiative forcing says that

Typically, radiative forcing is quantified at the tropopause in units of watts per square meter of the Earth's surface.

However this does not seem to explain why quantifying it "at the tropopause" makes sense, or what that means, since the measure given is measured on the surface. Does this imply that emissions below / above the tropopause are not considered contributing to radiative forcing? (I presume they are.)

Also, how come that emissions at greater heights force more? After all, at lower heights the same amount can cover a greater surface area at the same thickness / density. Maybe, the change in wavelength of incoming radiation is greater since the traveled distance is greater, and thus more is absorbed?

Lastly, does CO2 not ascend after being emitted at surface level, such that it will enter the stratosphere just as well as if it is emitted there? Or are there further factors partially mitigating this?

You can see I have too many questions, and find the Wikipedia articles very unrevealing / lacking.

Thank you!