As a "cloud person", I just want to add a few things to the description of how clouds affect the climate (and why high clouds have a wamring effect).
All clouds are white, so they all reflect sunlight back into space (during the day), cooling the Earth.
All clouds are (almost) black in the infra-red, meaning the amount of energy they emit in the infra-red is determined by their temperature. Colder clouds emit less energy.
Almost all clouds are colder than the surface beneath them, which means they emit less infra-red energy to space than a clear day would. This reduces the amount of energy the Earth emits to space, so warming the climate.
High clouds are colder than low clouds, so have a stronger warming effect.
In summary:
Low clouds - Reflect sunlight (cooling), don't trap much infra-red (little warming)- Net: Cooling effect
High clouds - Reflect sunlight (cooling), trap lots of infra-red (stronger warming) - Net: Warming effect
All clouds are white, so they all reflect sunlight back into space (during the day), cooling the Earth.
All clouds are (almost) black in the infra-red, meaning the amount of energy they emit in the infra-red is determined by their temperature. Colder clouds emit less energy.
Almost all clouds are colder than the surface beneath them, which means they emit less infra-red energy to space than a clear day would. This reduces the amount of energy the Earth emits to space, so warming the climate.
High clouds are colder than low clouds, so have a stronger warming effect.
In summary:
Low clouds - Reflect sunlight (cooling), don't trap much infra-red (little warming)- Net: Cooling effect
High clouds - Reflect sunlight (cooling), trap lots of infra-red (stronger warming) - Net: Warming effect