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.
When you get higher up into the atmosphere, the air pressure would decrease. The lower you get, the higher the pressure would be, seeing as you are deeper into the earth, and there is more room for the pressure to press down on you. The temperature also changes with the altitude; the higher you go, the colder the air becomes inside the troposphere.