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Summary of Lecture 1. Introduction to Earth’s atmosphere origin composition structure comparison with other planets Stefan’s law. Solar and Terrestrial Radiation. Sun ~ 6000 K UV/vis λ max ~0.6 μ m Solar flux =1370 Wm -2 S (1- α )/4= σ T E 4 Earth ~ 255 K IR λ max ~ 12 μ m.

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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


Solar and Terrestrial Radiation

  • Sun ~ 6000 K

  • UV/visλmax~0.6μm

  • Solar flux =1370 Wm-2

  • S (1-α)/4=σTE4

  • Earth ~ 255 K

  • IR λmax~ 12μm


DUV

UVb

UVa /

Visible

InfraRed

UVc

UV absorption


Absorption by atmospheric gases


Solar energy received


Notes:

  • Surface has Ts=288 K and radiates σTs4 = 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


Radiation Balance


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


JFM 2002 is clearly

the warmest ever

Temperature rise °C

Global temperatures 1860-2001


Change in extent of Arctic sea ice

Arctic sea ice extent, million km2


Rising CO2 levels


700

600

500

400

350

Carbon dioxide concentration

in the atmosphere, due to three emissions scenarios

Business as usual emissions

Constant 1990 emissions

50% reduction in emissions

CO2 concentration ppm


Global temperature rise

IPCC A1FI emissions

A2 emissions

B2 emissions

B1 emissions

Global temperature rise, degrees C


Hadley Centre

Components of sea-level rise


Met Office / Hadley Centre

A1FI emissions scenario

0

1

2

3

4

5

6

Pattern of annual temperature changes2080s relative to present day


winter

summer

Hadley Centre

Hadley Centre

°C

Temperature rise

Medium-high emissions scenario, 2080s


Met Office / Hadley Centre

A1FI emissions scenario

3

2

1

0.5

0.25

0

0.25

0.5

1

2

3

Pattern of annual precipitation changes2080s relative to present day


Medium-high emissions scenario, 2080s

winter

summer

Hadley Centre

Hadley Centre

Change in precipitation

%


Change in surface temperature

with forced THC collapse, but without change in greenhouse gases

Hadley Centre

Deg C


Carbon Cycle

  • photosynthesis

respiration


Predicted temperature rise

  • Assuming current levels of CO2 emission


Changes in precipitation predicted for doubling CO2 levels


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