Radiation

Discussion

introduction

Heat radiation (as opposed to particle radiation) is the transfer of internal energy in the form of electromagnetic waves. For most bodies on the earth, this radiation lies in the infrared region of the electromagnetic spectrum.

 
blackbody color by temperature
 
1,000 K 6,500 K  (daylight) 10,000 K
 
kelvin
temperature
radiant energy source
2.73 cosmic background radiation
306 human skin
500 household oven at its hottest
660 minimum temperature for incandescence
770 dull red heat
1400 glowing coals, electric stove, electric toaster
1900 candle flame
2000 kerosene lamp
2800 incandescent light bulb, 75 W
2900 incandescent light bulb, 100 W
3000 incandescent light bulb, 200 W
3100 sunrise or sunset (effective)
3200 professional studio lights
3600 one hour after sunrise or one hour before sunset (effective)
4000 two hours after sunrise or two hours before sunset (effective)
5500 direct midday sunlight
6500 daylight (effective)
7000 overcast sky (effective)
20-30,000 lightning bolt
Temperature (or effective temperature) of selected radiant sources
color temperature
K
incipient red heat 500–550 770–820
dark red heat 650–750 0920–1020
bright red heat 850–950 1120–1220
yellowish red heat 1050–1150 1320–1420
incipient white heat 1250–1350 1520–1620
white heat 1450–1550 1720–1820
Color Scale of Temperature Source: Handbook of Chemistry & Physics, Tenth Edition (1924)

"This table is the result of an effort to interpret in terms of thermometric readings, the common expressions used in describing temperatures. It is obvious that these values are only approximations."
color approximate temperature
K
faint red 930 500 770
blood red 1075 580 855
dark cherry 1175 635 910
medium cherry 1275 0690 0965
cherry 1375 0745 1020
bright cherry 1450 0790 1060
salmon 1550 0845 1115
dark orange 1630 0890 1160
orange 1725 0940 1215
lemon 1830 1000 1270
light yellow 1975 1080 1355
white 2200 1205 1480
Metal Temperature by Color Source: Process Associates of America
T (K) class λmax (nm) color name examples
30,000 O 100 blue naos, mintaka
20,000 B 150 blue-white spica, rigel
10,000 A 290 white sirius, vega
8000 F 360 yellow-white canopus, procyon
6000 G 480 yellow sun, alpha centauri
4000 K 720 orange arcturus, aldebaran
3000 M 970 red antares, betelgeuse
Spectral Classification of Stars

solar energy

greenhouse effect

History

The basic effect…

[slide]

Global temperature and atmospheric carbon dioxide trends match. The very long graph made popular by Al Gore in An Inconvenient Truth.

[slide]

Plot one against the other. The relation is approximately linear. Al Gore never did this one.

[slide]

Naturally occurring greenhouse gases whose concentrations are increasing due to human activities

Other naturally occurring greenhouse gases of lesser concern.

Greenhouse gases that do not occur naturally.

Indirect greenhouse gases

key infrared absorption bands in the atmosphere correspond to H2O, CO2, O3

molecule global warming
potential
(CO2 = 1)
atmospheric
lifetime
(years)
raditative
forcing
(W/m2)
radiative
efficiency
(W/m2ppb)
CO2 carbon dioxide 1 120 1.66 0.000014
CH4 methane 21 12 0.48 0.00037
N2O nitrous oxide 310 114 0.16 0.00303
CCl3F CFC-11 3,800 45 0.063 0.25
CF2Cl2 CFC-12 8,100 100 0.17 0.32
C2F3Cl3 CFC-113 4,800 85 0.024 0.3
CHClF2 HCFC-22 1,500 12 0.033 0.2
CCl4 carbon tetrachloride 1,400 26 0.012 0.13
CH3CCl3 methyl chloroform 146 5 0.0011 0.06
CHF3 HFC-23 11,700 270 0.0033 0.19
C2HF5 HFC-125 2,800 29 0.0009 0.23
C2H2F4 HFC-134a 1,300 14 0.0055 0.16
C2H4F2 HFC-152a 140 1.4 0.0004 0.09
SF6 sulfur hexafluoride 23,900 3,200 0.0029 0.52
SF5CF3 * 19,000 1,000 ? 0.59
H2O water, tropospheric ? ? ? ?
H2O water, stratospheric ? ? 0.02 ?
O3 ozone, tropospheric ? ? +0.35 ?
O3 ozone, stratospheric ? ? −0.15 ?
CO carbon monoxide ? 0.25 ? ?
H2 hydrogen ? ? ? ?
Global warming properties of selected greeenhouse gases
Sources: IPCC and others * trifluoromethyl sulphur pentafluoride

Temperatures are rising across the globe.

[slide]