summary of lecture 1
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Summary of Lecture 1
• Introduction to Earth’s atmosphere– origin– composition– structure– comparison with other planets
• Stefan’s law
44 1sT S
Solar and Terrestrial Radiation
Sun ~ 6000 K
UV/vis max~0.6m
Solar flux =1370 Wm-2
S (1-)/4=TE4
Earth ~ 255 K
IR max~ 12m
UV absorptionInfraRed
UVa /Visible
UVb
UVc
DUV
Absorption by atmospheric gases
Radiation Balance
Notes:• Surface has Ts=288 K and radiates Ts
4 = 400 Wm-2 (117 units).
• Atmosphere at 250 K radiates 220 Wm-2 (64 units), both up and down.
• 30% of surface radiation is reflected by the atmosphere (32 units), giving a total downward flux of 96 units.
• Non-radiative flux of 100 Wm-2 (30 units) drives the atmospheric circulation and weather
Seasonal net IR radiation
Global Climate
Net short, long and global radiation entering and leaving the top of our atmosphere measured by satellite.
Data are from the Earth Radiation Budget Experiment (ERBE)
Global Warming
Global temperatures 1880-2015
Change in extent of Arctic sea ice
Rising CO2 levels
0
50
100
150
200
250
300
350
1990 2000 2010 2020 2030 2040 2050 2060 2070 2080 2090 2100
700
600
500
400
350
CO
2 c
on
cen
trati
on
p
pm
Carbon dioxide concentrationin the atmosphere, due to three emissions scenarios
Business as usual emissionsConstant 1990 emissions50% reduction in emissions
Global temperature riseG
lob
al t
em
pe
ratu
re r
ise,
deg
ree
s C IPCC A1FI emissions
A2 emissionsB2 emissionsB1 emissions
Components of sea-level rise
Hadley Centre
Pattern of annual temperature changes
2080s relative to present dayA1FI emissions scenario
0 1 2 3 4 5 6
Met Office / Hadley Centre
Temperature riseMedium-high emissions scenario, 2080s
winter summer
°C
Hadley Centre Hadley Centre
Pattern of annual precipitation changes
2080s relative to present day
–3 –2 –1 1 2 3–0.5 0.5–0.25 0.250
A1FI emissions scenarioMet Office / Hadley Centre
Change in precipitation
%
winter summer
Medium-high emissions scenario, 2080s
Hadley Centre Hadley Centre
Change in surface temperature with forced THC collapse, but without change in greenhouse
gases
Deg C
Hadley Centre
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