Electromagnetic radiation includes Infrared Radiation (IR) and visible light. Both pass thru the atmosphere and are absorbed by the surface of the Earth and converted to kinetic energy (heat). This heat is emitted back outward as thermal radiation aka IR. This IR is reabsorbed by the denser atmospheric gases such as water vapor, carbon dioxide, methane, nitrous oxide, etcetera. This excites their structure and the resulting kinetic energy re-emits IR. Life on Earth is made possible by the capturing of enough IR to keep the biosphere warm enough to sustain life. As the heavier molecules in the atmosphere increase, the amount of IR also increases.