The phenomenon of a gradual increase in the average temperature of the earth is known as global warming.
It is caused by the release of greenhouse gasses in the atmosphere, including carbon dioxide, methane, and CFCs.
The troposphere, the lowest region of the atmosphere which stretches from Earth's surface up to a height of 6–11 miles, is where global warming, the phenomenon of rising average air temperatures near Earth's surface occurs primarily.
Most of Earth's clouds are present in this layer, which is also where most living creatures, their habitats, and weather occur.