Physics of Climate

1
Physics of Climate

• Recall
• Topic 2 Climate Sensitivity
• How does climate change when S changes?

2
Other Sensitivity How does climate change when
atmospheric composition changes?
Note that the scale of this is not the same as
our original b. One uses a change in C, the
other uses the full S.
Consider
From energy balance
Then
3
Other Sensitivity How does climate change when
atmospheric composition changes?
So
Why does this make sense?
For I ???Ts)4
For I ?????Ts
Note minus sign.
4
Lets use ?I 0
For I ???Ts)4
old new
This is bC for De cases
5
Instantaneous CO2 Doubling
CO2 Doubling gt??I - 4 W-m-2 What ?? gives
this? ?I ????(Ts)4 For Ts 288 K, ??????
?Ts ????
6
Lets use ?I 0 (Again)
For I ?????Ts
old new
?????Ts,o (A?A) (B?B)Ts,n
?Ts - (?A ?BTs,o)/(B?B)
This is bC for DA, DB cases.
?Ts - (?A ?BTs,o)/(B)
??I - 4 W-m-2
?A ?BTs,o - 4 W-m-2 (Eq. 1)
?A/A ?B/B
?Suppose
What are ?A ?B?
Hint (Eq. 1)/A
?Ts ????
7
Compare the two parameterizations
For I ???Ts)4 ?Ts 1.21 C
For I ?????Ts ?Ts 2.52 C
Why the difference?
8
Compare the two parameterizations
For I ???Ts)4 ?Ts 1.21 C
For I ?????Ts ?Ts 2.52 C
Why the difference?
Final note (empirical ?Ts) / (equiv BB ?Ts)
2.52/1.21 2.08 (empirical GF) / (equiv BB GF)
3.41/1.64 2.08
9
End Climate Sensitivity from Composition Change