Global Heat Budget

Question 1

Why does the earth’s surface absorb only 47% of the solar energy received at the edge of the atmosphere?

Answer 1

100% of incoming solar energy/short-wave radiation enters the atmosphere?

47% of solar energy is absorbed by the land and oceans, as they’re dark

23% is absorbed by air, clouds and dust in the atmosphere

30% is scattered to space from: dust particles, water vapour, reflection by clouds and reflection from the earth’s surface (the albedo effect is the extent to which light surfaces reflect light, and in areas like the north and south poles and in deserts, light ground reflects the light)

Question 2

Explain what happens to incoming solar radiation (how is it turned to heat?)

Answer 2

Light from the sun is shortwave light radiation and not actually heat. The heat we feel comes from light absorbed by the earth’s surface, converted into long wave radiation (10% of energy is used this way), which transfers into heat when coming from the earth’s surface = energy change.

7% of radiation stays in the ground and the soil.

Question 3

Variations in GHB :

The curvature of the earth and its effect on the concentration of the sun’s rays

Answer 3

At the equator, the sun’s rays hit the earth so there is a smaller area of earth and thus a more concentrated amount of solar radiation (1 mark), this means there’s more intense heating (1 mark)

Sun’s rays hit a larger, less concentrated area at the poles due to the curvature of the earth (1 mark), so heating is lesser (1 mark)

Question 4

Variations in GHB :

Amount of atmosphere the sun’s rays have to pass through

Answer 4

At the poles, there’s a larger distance of atmosphere to pass through due to the curvature of the earth, so there’s more time for atmospheric absorption and reflection of radiation (1 mark)

At the equator, radiation has less distance of atmosphere to pass through as it hits the earth at a 90º angle

Question 5

Variations in GHB :

The albedo effect (poles)

Answer 5

There’s more ice and thus more reflective surfaces at the poles, so the albedo effect (amount of light reflected by earth’s surface) is greater (1 mark)

Question 6

Variations in GHB :

The albedo effect (equator)

Answer 6

There are more dark rainforests and oceans that are a dark blue, so there’s more area of land for absorption of radiation to occur (1 mark)

Question 7

Variations in GHB:

Seasonal variations

Answer 7

Due to the tilt of the earth’s axis (1 mark), the distance between the poles and the sun changes throughout the year, giving seasons (1 mark) as the poles tilt away at certain times, and tilt towards the sun at others

The equator stays largely the same distance from the sun all year as it remains in the same position, so there are less seasonal variations (1 mark)