It is estimated that the Earth is losing about $5 \times 10^7 kg$ per year. Most of it due to hydrogen loss. I suppose this has an impact on the pressure of the atmosphere in general.
Thus, I am wondering how the pressure at sea level is varying over time from the Earth's birth up to now and how it could go. I.e. which model and equations are involved?
Edit: To clarify I am hinting at that a loss of mass of a gas can lead to a change in pressure at sea level. So I would expect the pressure to diminish over time from now and on.