Note the bright yellow incoming energy flux in this diagram. The sun supplies the earth with energy. Truism. Uncontested fact, except in the feverish brain of climate science deniers.
In a single
second the Earth absorbs 1.22 x 10^17 Joules of energy from the sun - over a thousand times more energy than was released by the Hiroshima fission bomb. Now the sun's energy is spread fairly uniformly over the earth's surface, but it is clear the planet would soon be burned to a crisp if that energy did not go somewhere.
And of course, it does go somewhere - right back into space (which is at a temperature of 0C). Which is were the atmosphere comes in - enough heat is trapped by GHG's to keep us comofrtably warm, as we have become accustomed for the last few ten thousands of years.
Otherwise, we would have a "climate" just like the moon, which had a mean temperature of -23C, but varies between -147C and +100C. Thank god for the atmosphere and greenhouse gases - but don't let's have too much of them.
And for deniers - is that
really so hard to understand?