So, it seems we have determined (about a century after the fact) that neither nitrogen or oxygen are greenhouse gases, neither are involved, under atmospheric conditions, in the emission of energy to space. Without GHGs in our atmosphere, it would be completely transparent to radiated IR which would shoot directly to space leaving the Earth's surface 33C cooler than it is. That -50F Arctic air mass that just passed through would have been about -110F. Instead, within a few meters of the Earth's surface, the GHGs present (CO2, CH4, NO2, H2O) absorb a significant portion of the infrared that the surface radiates. Slowing the release of that infrared raises the equilibrium temperature of the surface, the oceans and the atmosphere. They call that the greenhouse effect.