How does warmth get into the earth's atmosphere without getting out?

Question

If CO2 is keeping warmth in but how can it get in in the first place without being reflected into space.

Answer 1

Well the same way it gets into a green house and doesn't get back out.  It arrives as infrared waves and upon encountering something solid and mostly dark it is converted into heat which is then trapped by the atmosphere or in the case of a green house, by the glass.

Answer 2

The incoming solar radiation is a short-wave radiation which does not heat the atmosphere while arriving at the earth's surface.On reaching the surface,part of the radiation is absorbed and part reflected back into space,the proportions depending upon the nature of the surface and the inclination of the incident solar beam.Solar radiation that is absorbed at the surface is converted into heat.Part of this heat energy is radiated out as long-wave radiation and part carried upward as sensible heat by convection thereby heating the atmosphere from the bottom.These heat radiations only are absorbed and trapped by CO2 and water vapour keeping the atmosphere near the surface warmer.