A simple climate model

• Fs = 1375 W/m2, tube area pa2

• ~30% reflected away into space: albedo a = 0.3

• ~70% emitted as thermal infrared F0, from area 4pa2

• F0=¼Fs(1-a) » 240 W/m2

• “effective temperature”, Te given by: sTe4=F0

• gives Te = 255K, lower than observed Ts = ~285K

• why? - greenhouse effect