Carbon Cycle

Carbon moves from the atmosphere to plants, from plants to animals,  from plants and animals to the ground, from living things to the atmosphere, from fossil fuels to the atmosphere when fuels are burned.
Carbon dioxide is a greenhouse gas and traps heat in the atmosphere. Without it and other greenhouse gases, Earth would be a frozen world.

http://www.windows2universe.org/earth/Water/co2_cycle.html

Temperature Inversion

Temperature inversion layers, also called thermal inversions or just inversion layers, are areas where the normal decrease in air temperature with increasing altitude is reversed and air above the ground is warmer than the air below it. Inversion layers can occur anywhere from close to ground level up to thousands of feet into the atmosphere.

http://geography.about.com/od/climate/a/inversionlayer.htm