Earth Earth ’ ’ s radiative balance s radiative balance or, how I learned to stop worrying and love the greenhouse effect or, how I learned to stop worrying and love the greenhouse effect If the Earth had no atmosphere: T T 4 = S / 4 (1 — A) T = 255 T = 255 K K -18 ˚C -18 ˚C 0 ˚F 0 ˚F Albedo (reflectivity) Solar constant (1370 W/m 2 ) Stefan-Boltzmann constant (5.67x10 -8 ) reflected Absorbed and re-radiated as heat
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Earth’s radiative balance or, how I learned to stop worrying and love the greenhouse effect If the Earth had no atmosphere: T T 4 = S / 4 (1 — A) T =
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EarthEarth’’s radiative balances radiative balanceor, how I learned to stop worrying and love the greenhouse effector, how I learned to stop worrying and love the greenhouse effect
If the Earth had no atmosphere:
TT4 = S/4(1 — A)
T = 255 KT = 255 K
-18 ˚C-18 ˚C
0 ˚F0 ˚F
Albedo (reflectivity)
Solar constant (1370 W/m2) Stefan-Boltzmann constant
(5.67x10-8)
reflected
Absorbed and re-radiated as heat
288 - 255 = 33 ˚ of 288 - 255 = 33 ˚ of ‘‘normalnormal’’ greenhouse warming greenhouse warming
Actual surface
No atmosphere
Sunlight Infra-red radiation
Air
0
-0.4
0.4
1900 1940 19801860
Te
mp
era
ture
ano
mal
y (˚
C)
Global Temperatures for the last 150 yearsGlobal Temperatures for the last 150 years(5-year running average; as of ~2005)(5-year running average; as of ~2005)
Civil war
Model T
World War II
Al Gore inventsthe internet
After Jones and Wigley, 1980
“ . . . a global deterioration of climate, by order of magnitude larger than any hitherto experienced by civilized mankind, is a very real possibility and indeed may be due very soon.”
Climate change in the age of DiscoClimate change in the age of Disco
The last ~10 years: another plateau resembling ~1950
Currently favored explanation of the plateaus is thatthese are periods when accumulated heat gets
preferentially stored in ocean instead of atmosphere…
Warming has a strong geographic bias(2000-2009 avg. vs. 1950-1980 mean)
±2.5 ˚C scale
A long-suspected driving force — rise in COA long-suspected driving force — rise in CO22
Global average 1700-2000 AD
Mauna Loa 1958-2004 AD
The COThe CO22 Greenhouse Effect Greenhouse EffectWhat should physical principles lead me to expect of global warming?What should physical principles lead me to expect of global warming?
Complications • Solar ‘constant’ is a variable• Water-vapor feedback• Albedo
• Ice• Clouds• Aerosols and dust• Ground cover
33 ˚ of warming = 20˚ from H2Ov + 10 ˚ from CO2 + 3 ˚ from other things
COCO22 has risen 10 has risen 10’’s of %, so T shoulds of %, so T should
have risen by a degree or morehave risen by a degree or more
Arrhenius, 1896
Doubling CO2 = 5-6 ˚C warming
Cylon invasion happens here
Reid, 1999; by way of www.oar.noaa.gov
Sunspots and early 20th century temperatures
So what factor is to blame for 20So what factor is to blame for 20thth century T rise? century T rise?Wrong question — lots of things are to Wrong question — lots of things are to ‘‘blameblame’’ but some but some
are more important than others, and at different timesare more important than others, and at different times