% A crude energy balance of the Arctic for present-day values:

epsilon=0.6;
H=3.5e15;
R=6600e3;
A=abs(2*pi*R^2*(cosd(0)-cosd(30))); % co-latitude!
alpha=0.55;
S=200; % solar radiation over the Arctic in W/m^2
sigma=5.670374419e-8;
Delta_F_R=0.0;  % CO2, add 4 W/m^2 per doubling with H2O, 2 W/m^2 without.

T=((H/A+Delta_F_R+(1-alpha)*S)/((1-epsilon/2)*sigma))^0.25;
T_C=T-273.15;
fprintf("T=%4.3g K, T (°C)=%4.2g\n",T,T_C)

% output: Area=3.7e+13 m^2, T= 261 K, T (°C)= -12
