All flesh is made from the carbon dioxide in the air. Photosynthesis and respiration would balance were it not for death. Some cellular carbon is buried in the soil or sinks to the bottom of the sea. Thus, release of oxygen in photosynthesis exceeds the release of carbon by respiration. Oxygen in the upper atmosphere shields us from UV radiation which blasts double-oxygen molecules apart that may then recombine or form ozone. This raises the temperature in the upper stratosphere to 28 degrees F, up from -71 F below that layer. Weather thus cannot rise through this warmer top layer, creating the anvil-shaped tops on the largest thunderheads where they hit the stratosphere.
Over 78% of air is nitrogen - essential for life/proteins. Without decay and decomposition, the atmosphere would have been devoid of nitrogen long ago.
Air is set in motion by the sun heating areas near the equator more than at the poles. Rising air near the equator flows north and cools, lowering the pressure beneath it. Colder air from the poles is denser, flows south, and warms as it goes. Because the Earth spins while this occurs the air is deflected west of east, depending on whether it is in the northern or southern hemisphere, and the results quickly become unpredictable and ever-shifting.
Growing air pollution first masked the effects of climate change - temperatures declined slightly from 1945 til the 1970s.
Dust carried by the trade winds from Africa supplies much of the iron and calcium and over half the phosphorus the ocean's plankton require. The dust reaches Brazil, the Caribbeans, the SE U.S., etc. About one billion tons/year, mostly from the Sahara and nearby deserts. Little windstorms in the desert (no rainstorms) lift the fine soil, microbes, and spores into the upper air where it is move NE to SW across the Atlantic. Similarly with the Gobi desert - to eg. Hawaii.
There are 10 - 15 thousand spores in the average cubic yard of air, rising to as high as a million after a summer rain. These fungi, when not decaying the dead, are mostly responsible for plant diseases, though sometimes problems for humans as well (eg. athlete's foot, St. Anthony's Fire - serious problem, now prevented by treating rye plants). Bacteria, when aloft, create condensation nuclei.
EPA analyses post 9/11 near the WTC used samples from the ground, instead of from the air. Even so, the pH found was high (9 - 11), and long, slender fibers that could lodge in the lungs were present. Ten years later 43 of the 60 - 70 thousand site workers have incurred medical problems and biopsies have found silicates, asbestos, and carbon nanotubes in their lungs.