Temperatures can reach lows of -90 degrees Celsius in the mesosphere, making it the coldest layer of the earth's atmosphere. The mesosphere extends above the stratosphere and ranges from 50 km to 87 km above the surface.
The troposphere is the part of the atmosphere that reaches Earth's surface that allows life to flourish. It only extends 11 km up, where it meets the stratosphere. Temperatures are warmer in the stratosphere, because of higher amounts of ozone. However, the area that extends above 50 km, the mesosphere, has decreasing temperatures. This layer has less solar heating and higher levels of CO2, which increases the rate of cooling. This area of the atmosphere is the coldest place on Earth.