Imagine that our sun brightens by 1% simultaneously. a) How long would it take f
ID: 1119 • Letter: I
Question
Imagine that our sun brightens by 1% simultaneously.
a) How long would it take for the earth to reach its new equilibrium temperature? is this longer or shorter than the time it would take mars or mercury to reach their respective equilibrium temperature?how would the calculated radiative forcing change if the brightening takes place over 1,000 years instead of simultaneously?
b) What radiative forcing does this change correspond to?
c) Approximately how much warming would this brightening cause eventually cause?
d) How would the calculated radiative forcing change if the brightening takes place over 1,000 years instead of simultaneously?
Explanation / Answer
a)There are many refinements we could make to this model. One of the more interesting is to put a temperature dependence on the albedo. As the temperature of the earth decreases, more of the water on the planet will freeze, which will increase its albedo (since the albedo of ice is about 0.6 compared to about 0.32 for land). We could account for this in the following way
if T < TIce, alpha= alphaIce
if T > TLand, alpha= alphaLand
otherwise, alpha= alphaIce + (alphaLand- alphaIce) *(T-TIce)/(TLand-TIce)
Where the constants are defined as
alphaIce Albedo of Ice (0.6)
TIce Global Temperature at which entire Earth freezes (-10 C)
alphaLand Albedo of Land (0.32)
TLand Global Temperature at which entire Earth melts to current state with small polar ice caps) (+10 C)
b)Radiative forcing by a climate variable is a change in Earth