[fatty28uk (OP)]

Does the use of pneumatic tyres on motor vehicles etc have any effect on global air pressure.

[CliffordK]

Is your question, say putting 35 PSI of air in a tire taking it out of the atmosphere, so there is less air in the atmosphere? 

With the majority of our atmosphere about 100 miles thick, there is a lot more air than what is in a few tires.  The affects would be extremely minimal, and easily masked by other changes in air pressure through temperature, wind and etc. 

On an annual basis, we burn billions of tons of hydrocarbons, and over the last few centuries, humans have actually managed to increase the carbon dioxide in the air from about 0.028% to about 0.040%, or about a total change of 0.012%. 

By doing so, we've also likely decreased the oxygen content in the air from about 20% down to 20% minus 0.012%.  Actually, since water is also formed, and much of the CO₂ is absorbed in the ocean, we've probably lost at least double that amount of oxygen, or more than 0.025%.  Very sensitive instruments should be able to pick up the oxygen decrease, but it would be difficult to measure because of the annual respiration cycles of plants and trees, oxygen released from a warming ocean, and potential differences between urban and rural areas being blown around by the wind.

CO₂, of course, is a gas, but we probably have lost more air through making water from burning hydrocarbons than we have lost through filling all of the tires in the world.

[fatty28uk (OP)]

Thanks for your response.
It was something that had rattled around in my head for a while.  []