Temperatures vary as you rise in altitude.
The Earth's atmosphere consists of five layers in order from closest to the surface to furthest away: troposphere, stratosphere, mesosphere, thermosphere and exosphere. The average temperature varies from layer to layer and also within each layer. Several reasons exist for the variance of temperature within layers and from layer to layer.
Altitude
Altitude, or the distance from the layer of the atmosphere to the earth's surface, impacts temperature. The layer nearest to the earth's surface, the troposphere, is warmer than the next layer, the stratosphere, in overall temperature. The troposphere's warmth is not uniform; within the troposphere there are temperature changes due to altitude. The average temperature on the earth's surface at the bottom of the troposphere is 62 degrees Fahrenheit while the average temperature at the top of the layer, which ranges from four miles at the poles to 12 miles at the equator, is minus 60 degrees Fahrenheit. The top of the troposphere marks the location where altitude no longer causes the temperature to drop.
Ozone
The next layer of the atmosphere above the troposphere, the stratosphere, begins with temperatures of minus 60 degrees Fahrenheit. Unlike the troposphere, the temperature does not decrease with altitude, but increases. This increase results from the effects of the ozone and the heat it produces. The stratosphere continues to heat up until the temperature reaches 5 degrees Fahrenheit at the top of the layer, or 31 miles above the earth's surface. This makes the stratosphere warmer overall than the next layer above it, the mesosphere.
Solar Radiation
The mesosphere, which covers the distance from 31 miles to 56 miles above the surface, is the coldest layer. Above the mesosphere, in the thermosphere, the temperature rises due to solar radiation from ultraviolet and X-ray radiation from the sun. The thermosphere extends up to 375 miles and represents the upper atmosphere. Beyond it is the exosphere and outer space. This combination of radiation from the sun sends temperatures up to 3,600 degrees Fahrenheit near the top of the stratosphere. The air remains very thin, but the molecules become very hot.
Earth's Heat
Other than the extreme temperatures at the high levels of the thermosphere, the warmest part of the atmosphere is the air in the troposphere at sea level, particularly in the tropics surrounding the equator. This temperature is due to the earth retaining the heat from the sun; it explains why it is warmer during the day than at night. The air at sea level contains more oxygen and is thicker than anywhere else and retains heat.
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