The climate impact of air travel is often divided into CO2 emissions and "high altitude effects" like that of water vapour and cloud formation. The effect of the emitted CO2 is cummulative, as CO2 has a high retention time in the atmosphere. On the other hand, as I have understood it, the high altitude effects are more short lived. Their impact on temperature are determed by current levels of air travel, and not past.
How can the size of these two effects be compared to each other or to other sectors such as travel by car? Is there any videly accepted method for this? It seems a bit like apples and oranges to me.
I know about GWP, that uses a somewhat arbitrary timeframe of 100 years. Is and can that be used here? I have also heard about RFI, but I am unsure how that works or is applied to this.