Climate change can have a major affect on pressure in the long run. Rising ocean can cause higher pressure and warm temperature can also bring the pressure up.
This website tell the average pressure on earth. The pressure on earth depends on where you are in the world.
The pressure at any level in the atmosphere can be determined by this equation inside of this link.
This shows aviation for casts and tells about pressure on earth and in the skys.
A team of scientists has created the highest static pressure in a lab