Cloudy nights are warmer compared to clear cloudless nights because clouds reflect back heat given off by Earth.

Explanation:

Clouds act as a barrier to the outgoing thermal radiation emitted by the Earth`s surface. They reflect a portion of this thermal radiation back towards the surface, effectively trapping some of the heat. This phenomenon is known as the greenhouse effect.

Clouds are composed of tiny water droplets or ice crystals, and these particles have the ability to reflect and scatter incoming solar radiation as well as outgoing thermal radiation. When the Earth`s surface cools down during the night, the presence of clouds prevents the thermal radiation from escaping into space. Instead, the radiation is reflected back towards the surface, contributing to the warming effect.

On the other hand, clear cloudless nights allow more of the outgoing thermal radiation to escape into space, resulting in cooler temperatures compared to cloudy nights.

It`s important to note that clouds also have other complex effects on the Earth`s climate system, such as absorbing and re-emitting radiation at different wavelengths and affecting the distribution of moisture and energy. However, the main reason why cloudy nights are warmer is due to the reflection of heat back towards the Earth`s surface.