Global Energy Balance

2 2 4(1 ) 4 eR S A R T

Te/K Tm/K Tsurf/KVenus 227 230 750Earth 256 250 280Mars 216 220 218[Jupiter 98 130 134 ]

-2

Solar constant at earth orbit:

1370 WmS

Simple Greenhouse analogy

4 41 12 2

1/ 4

unrealistic idealisation: all radiation scattered by a single layer:

/ 2 1.2

e e S S

S e

T J J T

T T

eJ

eJSJ

Infra-red emission spectrum (over sunny mediterranean)

Atmospheric profile

DR Leadley

More on atmospheric profiles

2 2N O

0

Force balance is a good approximation:

Ideal gas applies: ; 0.8 0.2 .

Isothermal approx: exp

- reasonable insight into rapid fall-off of , wi

dp gdh

pmn m m m m

kT

mghT const p p

kT

p

th , but not right for .

Still air: radiation balance calculations for rapid fall off with height

Stability limit against convective rise:

adiabatic law

atmospheric m

p

h T

T

dT dpc RT p

T

ust fall off more slowly else unstability:

air pocket rises less cool than surroundings less dense rises more..

Troposphere and Stratosphere

: heated from below:

convective activity dominates heat transport; radiation not balanced;

profile close to adiabatic limit .

Evaporation/condensation o

p

Troposphere

dT dpc RT p

f water vapour boosts effective ,

making the profile even more shallow than dry air.

: partially heated from above:

Ozone adsorbs incoming solar UV, en

pc

Stratosphere

ergy re-radiated in IR;

stable radiation balance profile, no convection.

: Boundary between T and S impressively sharp,

but it does move up and down with night and day and

Tropopause

season.

Tropopause views

CalculatedRadiation-Convection temperature profiles

Infra-red emission spectrum (over sunny mediterranean)

Digest of the emission spectrum

What matters, for each part of the spectrum, is the

temperature at the height above which the atmosphere is transparent.

• Water (vapour) absorbtion bands: saturated as far as the vapour rises. Eq’m vapour pressure strongly controlled by T, so temperature of vapour emission somewhat buffered.

• !!Water clouds are much more delicate to assess ……

• CO2 bands: saturated to Stratosphere. Average T of emission only sensitive at edge of these bands, but these are quite broad.

• !!This does assume the stratosphere temperature is insensitive. Under query.

• Atmospheric windows: anything which does scatter IR here will have a strong effect per molecule. CH4, CFC’s act in this way.

More complete radiation balance

1370 / 4

Shifted radiation balance

Temperature Selection including albedo

Two thousand year temperature record 2005

The Globe is Warming (IPCC TS2001) “Hockey Stick”

Sea Levels are rising … (IPCC TS2001)

Planetary temperature profiles