the coldest region of the atmosphere

The coldest region of the atmosphere is the Mesosphere. Here's a step-by-step explanation:

1. The Earth's atmosphere is divided into five main layers: the Troposphere, the Stratosphere, the Mesosphere, the Thermosphere, and the Exosphere.

2. The Troposphere is the layer closest to Earth's surface where we live and weather occurs. The temperature in this layer decreases with altitude.

3. Above the Troposphere is the Stratosphere, where the ozone layer is located. The temperature in the Stratosphere increases with altitude due to the absorption of UV radiation from the Sun.

4. Above the Stratosphere is the Mesosphere. The temperature in the Mesosphere decreases with altitude. The top of the Mesosphere, called the mesopause, is the coldest part of Earth's atmosphere with temperatures averaging about minus 85 degrees Celsius.

5. Above the Mesosphere are the Thermosphere and the Exosphere, where the temperature increases with altitude. However, despite the high temperatures in these layers, they would not feel hot to a human due to the extremely low pressure and density.

So, the Mesosphere is the coldest region of the atmosphere.