L2 - Radiation and the GHG effect

Question 1

What are the main greenhouse gases?

Answer 1

Water vapor, carbon dioxide, ozone, methane, CFCs, HFCs, N2O, SF6

Question 2

What would Earth’s surface temperature be without greenhouse gases?

Answer 2

-18 deg C

Question 3

What is Earth’s surface temperature with greenhouse gases?

Answer 3

15 deg C

Question 4

What is the mean temperature increase due to the greenhouse effect?

Answer 4

33 deg C

Question 5

What type of radiation does the Sun emit?

Answer 5

high-temperature sources (shortwave radiation)

Question 6

How does solar radiation interact with Earth’s atmosphere?

Answer 6

Some is absorbed by clouds and gases, most passes through and warms the surface, some is reflected back into space

Question 7

What happens to infrared radiation emitted by Earth?

Answer 7

Some is absorbed and re-emitted by greenhouse gases, warming the surface and atmosphere

Question 8

What is the equation for electromagnetic radiation?

Answer 8

vλ = c

Question 9

What does each symbol in vλ = c represent?

Answer 9

v = frequency, λ = wavelength, c = speed of light

Question 10

Which types of radiation carry the most energy per wave?

Answer 10

X-rays

Question 11

What objects emit radiation?

Answer 11

All objects with a temperature greater than 0 K

Question 12

What are the two key radiation laws?

Answer 12

Stefan-Boltzmann Law and Wien’s Law

Question 13

What does Stefan-Boltzmann Law state?

Answer 13

Total energy emitted by a black body relates to temperature: I(T) = σT⁴

Question 14

What does Wien’s Law describe?

Answer 14

The peak wavelength of emission depends on temperature: λ_max T = 2.897 x 10⁶

Question 15

How does wavelength change with temperature?

Answer 15

Higher temperature → shorter wavelengths; Lower temperature → longer wavelengths

Question 16

What is Earth’s equilibrium temperature without greenhouse gases?

Answer 16

255K (-18°C)

Question 17

What is Earth’s observed surface temperature?

Answer 17

288K (15°C)

Question 18

What is Earth’s albedo?

Answer 18

30% of incoming solar radiation is reflected

Question 19

How much solar radiation is absorbed by land and water?

Answer 19

51%

Question 20

What percentage of absorbed radiation is re-emitted as infrared radiation?

Answer 20

15%

Question 21

What is the role of greenhouse gases in radiation balance?

Answer 21

They trap longwave radiation, leading to atmospheric warming

Question 22

What is the difference between absorption and emission?

Answer 22

Absorption: A molecule absorbs energy and moves to a higher state

Emission: A molecule drops to a lower energy state and emits a photon

Question 23

How do different molecules absorb radiation?

Answer 23

They absorb radiation at specific wavelengths corresponding to energy level differences

Question 24

What is the equation for photon energy?

Answer 24

E = hf = h/λ

Question 25

What is the greenhouse effect?

Answer 25

GHG absorb and re-emit infrared radiation, warming Earth's surface

Question 26

do warmer or colder objects emit more intensely

Answer 26

warmer

Question 27

how do warmer objects emit energy compared to colder objects

Answer 27

- warmer = high proportion of energy emitted at shorter wavelength - colder = longer wavelength

Question 28

what is a black body

Answer 28

absorbs all radiation falling on it and re-emits it as a function of its surface temp 

Question 29

where is the suns energy concentrated in a narrow wavelength region

Answer 29

0.4 and 0.7 microns (visible part of spectrum)

Question 30

how do all bodies radiate energy

Answer 30

as electro-magnetic radiation 

Question 31

The Stefan-Boltzmann law relates how the total energy emitted by a black body relates to the temperature by I(T) = σT4 , what does this equation stand for?

Answer 31

I = energy per unit area emitted per second (watts m-2) T = blackbody temp (K) σ = Stefan-Boltzmann constant (5.67 x 10-8 m-2 K-4)

Question 32

what is the difference between solar and terrestrial radiation

Answer 32

solar= 5900K, short wave terrestrial = 288K , long wave

Question 33

what is radiation the primary energy source for

Answer 33

atmospheric and ocean circulation and for all life on Earth

Question 34

what is the albedo of clouds

Answer 34

- very dark = albedo close to 0% - very light =

Question 35

what are the GHG effects of solar radiation?

Answer 35

- some solar radiation absorbed by Earth's surface and atmosphere  - Earth and atmosphere emit infrared radiation - GHG absorb some of this infrared radiation in all directions - Earth absorbs downward directed infrared radiation - Result = warmer surface temperature = 288 K rather than 255K