If a planet has no atmosphere, all of the sunlight which strikes it reaches the surface, and usually, 90% or more of that is absorbed, and 10% or less is reflected back into space. However, if the planet has an atmosphere, particularly a thick, cloud-filled atmosphere, part of the sunlight will be reflected into space before even reaching the surface. The percentage of light reflected by a planet is referred to as itsalbedo, and subtracting that from 100% tells us how much energy is absorbed by, and heats up, the planet. So, definitely If there was no atmosphere, Earth would have been hotter.
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Apoorva Arora
IIT Roorkee
askIITians Faculty
