Impacts of high-altitude emission of greenhouse gases (GHG) compared to sea level GHG emissions
I think you may be confusing two separate, but related, issues.  Aircraft emissions at high altitudes are a concern for the ozone layer, because the NOx that is emitted by aircraft can catalytically destroy ozone.  Supersonic aircraft fly higher up in the stratosphere than a typical jet, and thus can harm the ozone layer more effectively.  The ozone layer is related to climate change, which is perhaps why you are mixing two issues.  For the most part, aircraft greenhouse gas emissions are not a concern simply due to the altitude they are emitted.  Instead, aircraft GHGs are a concern because they are long-lived in the atmosphere and well-mixed, causing "global" warming.  Furthermore, aircraft emissions are expected to continue increasing for decades.