Earth's energy balance Flashcards
What is the temperature of an object dependent on?
Amount of energy it emits and receives
How does Earth give out heat?
Radiation (Earth is in a vacuum so can’t conduct heat by conduction or convection)
Solar radiation is …
shortwave
Terrestrial radiation is…
longwave (infrared)
The hotter the object…
The more the spectrum is shifted to short wavelengths
What is the average incoming solar flux over all latitudes?
342 Wm^-2
What is Earth’s global average albedo?
0.3
What would the temperature of the Earth be if there was no atmosphere?
-18ºC
How much of a warming effect does the natural greenhouse effect have?
Warming of 33ºC
What is emissivity?
The ratio of actually emitted to maximum possible radiation emitted
What is the average global emissivity?
0.61
What is bare Earth temperature with albedo estimated at?
-18ºC
How does the Earth stay in radiative equilibrium when emissivity is decreased?
Earth must radiate at higher temperatures
[E=εσT^4]
What temperature would earth be without the heat source of the sun?
-269ºC
What is terrestrial radiation?
Thermal radiation emitted by earth
What does radiative equilibrium mean?
Energy absorbed by earth is equal to energy emitted by earth to space
If earth is in equilibrium with incoming solar radiation, E emitted should be equal. This would make the earth 5ºC. What does this calculation not consider?
Greenhouse effect and the albedo of the earth’s surface and clouds
What is albedo?
Reflectivity of solar radiation by earth and the atmosphere
Even when the radiative balance equation is solved fairly accurately for each latitude band of Earth, the temperature distribution is still not right. Why?
Ignores the transport of heat by weather systems and ocean circulation, which reduces the temperature contrast
