# heat budget of planet earth

## the heat budget

Because solar energy continually enters Earths atmosphere and ground surface, is the planet getting hotter? The answer is no (although the next section contains an exception), because energy from Earth escapes into space through the top of the atmosphere. If the amount that exits is equal to the amount that comes in, then average global temperature stays the same. This means that the planets heat budget is in balance. What happens if more energy comes in than goes out? If more energy goes out than comes in? To say that the Earths heat budget is balanced ignores an important point. The amount of incoming solar energy is different at different latitudes. Where do you think the most solar energy ends up and why? Where does the least solar energy end up and why? See the Table 1.1. Equatorial Region Polar Regions Day Length Nearly the same all year Night 6 months Sun Angle High Solar Radiation High Albedo Low Low Low High Note: Colder temperatures mean more ice and snow cover the ground, making albedo relatively high. The difference in solar energy received at different latitudes drives atmospheric circulation.

## heat at earths surface

About half of the solar radiation that strikes the top of the atmosphere is filtered out before it reaches the ground. This energy can be absorbed by atmospheric gases, reflected by clouds, or scattered. Scattering occurs when a light wave strikes a particle and bounces off in some other direction. About 3% of the energy that strikes the ground is reflected back into the atmosphere. The rest is absorbed by rocks, soil, and water and then radiated back into the air as heat. These infrared wavelengths can only be seen by infrared sensors. Click image to the left or use the URL below. URL:

## instructional diagrams

No diagram descriptions associated with this lesson

## questions

only this much of the solar radiation reaches the surface of the earth.

``````a) three-fourths

-->  b) half

c) one-fourth

d) two-thirds
``````

the equatorial regions albedo is low because the region is heavily forested.

``````-->  a) true

b) false
``````

the amount of incoming solar radiation is the same at all latitudes.

``````a) true

-->  b) false
``````

night and day each last 6 months in the polar regions.

``````-->  a) true

b) false
``````

about 90% of the solar radiation that strikes the top of the atmosphere is filtered out before it reaches the ground.

``````a) true

-->  b) false
``````

what happens to the suns radiation that strikes the ground?

``````a) it is reradiated as heat.

b) it is reflected back into the atmosphere.

c) it is absorbed by rocks and soil.

-->  d) all of these.
``````

why is the albedo in the polar regions high?

``````-->  a) the polar regions have a lot of snow and ice.

b) the polar regions have a lot of vegetation.

c) the polar regions have a lot of open dirt and rock.

d) all of these.
``````

where is the number of day and night hours closest to equal all year?

``````-->  a) the equator.

b) the north pole.

c) the south pole

d) the tropic of cancer and the tropic of capricorn.
``````

why isnt earths heat budget balanced?

``````a) because the amount of outgoing heat is greater than the amount incoming heat.

b) because the amount of solar radiation is not equal at different latitudes.

-->  c) because the amount of incoming heat is greater than the amount outgoing heat.

d) because the amount of solar radiation is the same at different latitudes.
``````

if more heat enters the earth system than leaves it, then

``````a) the planet will cool.

b) more heat will need to leave the system.

c) more heat will need to enter the system.

-->  d) the planet will warm.
``````

## diagram questions

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