Atmospheric carbon dioxide is the primary source of carbon in life on Earth and its concentration in Earth's pre-industrial atmosphere since late in the Precambrian was regulated by photosynthetic organisms and geological phenomena.
At about 55 km, the mesosphere begins. In the mesosphere, the temperature decreases with height again, because there is very little ozone to warm up the air. Finally, the mesopause divides the mesosphere from the thermosphere, which is the section of the atmosphere higher than 90 km. In this region, the temperature increases again. This time, it is molecular oxygen (O2) that causes the temperature increase.
The global increase in temperature is mainly due to the release of greenhouse gases. Greenhouse gases causes the blanket of air surrounding the earth to thicken, thus warming up the earth. The byproducts of the nitrogen cycle produce greenhouse effects, specifically in agricultural fields.