In terms of impact there's a generally accepted ~2.7X multiplier applied to flight emissions:
"Among the reasons for this focus is that these emissions, because they are made at high altitude, have a climate impact that is commonly estimated to be 2.7 higher than the same emissions if made at ground-level." [0]
So you can look at 2-3% of co2, or you can look at impact and if we use the co2 proportion as a proxy of overall emissions, ~8% in terms of impact - and growing fast.
I wonder what the emissions from a methane powered suborbital BFR is compared with a 16 hour flight, especially if that methane was generated from CO2 extraction from the air using renewable sources of electricity.
"Among the reasons for this focus is that these emissions, because they are made at high altitude, have a climate impact that is commonly estimated to be 2.7 higher than the same emissions if made at ground-level." [0]
So you can look at 2-3% of co2, or you can look at impact and if we use the co2 proportion as a proxy of overall emissions, ~8% in terms of impact - and growing fast.
https://en.wikipedia.org/wiki/Hypermobility_(travel)