Greenhouse Effect

What you are seeing: a 3D Earth in radiative balance with the Sun. Solar shortwave (cyan) streams in, the surface re-emits as IR (red), and a fraction of the IR is trapped by the atmospheric greenhouse layer. The equilibrium surface temperature T_surf is set by the balance. Drag to orbit, scroll to zoom

Figure 1. 3D Earth + Sun in radiative balance. Cyan photons = incoming visible; red = outgoing IR; trapped IR re-absorbed by atmospheric layer warms surface. Right: T_surf = T_eff (2/(1+tau))^(1/4) curve over tau_LW. Method: single-layer grey-atmosphere energy balance; log-CO2 parametrisation tuned to 3 K / doubling.

presetcurrent

CO2 (ppm)420

albedo A0.30

photon density80

WHAT TO TRY

Step through the presets from pre-industrial to 2x CO2 to Venus: more greenhouse gas raises the longwave optical depth tau_LW, trapping outgoing IR and lifting the surface temperature above the bare T_eff.
Raise the CO2 directly: the surface warms while the effective radiating temperature seen from space barely changes, the fingerprint of the greenhouse mechanism.
Raise the albedo toward Snowball Earth: more sunlight is reflected, the planet cools, and the ice-albedo feedback can tip it into a frozen state.