Energy absorbed =
Energy radiated
\(L/(4pd2))pr2 = 4pr2sT4
\T = 278 (L€/d2AU)1/4 K
Greenhouse effect :
Earths atmosphere relatively transparent
to solar radiation (heating)
but re-radiation (cooling) in infrared is impeded (photons absorbed by CO2, H2O)
For Venus, greenhouse effect is enormous
due to CO2, T = 600K (could
happen at Earth)