Earth’s Energy Budget

• What exactly is a budget?

• Do you or your parents have a budget?

Definition: budg·et

an estimate of income and expenditure for a set period of time

Earth has an “Energy Budget”

The Earth does not have an “income” but it does have an energy flow into and out of the Earth.

Earth receives energy from the sun through electromagnetic radiation.

Remember that ‘radiation’ does not need a medium to flow through, so it can travel through the vacuum of space directly to Earth.

Everything that has a temperature gives off electromagnetic radiation (light).

The sun is extremely hot and has a lot of energy to give, so it gives off shortwave radiation because shortwave radiation contains higher amounts of energy.

The earth is much cooler, but still emits radiation. Earth’s radiation is emitted as longwave because longwave radiation contains a smaller amount of energy.

This image is an atmospheric window of the wavelengths that enter our atmosphere. Our atmosphere is transparent to radio waves, visible light, and some infrared and UV radiation.

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.

Of all the sunlight that passes through the atmosphere annually, only 51% is available at the Earth's surface to do work. This energy is used to heat the Earth's surface and lower atmosphere, melt and evaporate water, and run photosynthesis in plants.

Let’s calculate Earth’s Energy Budget!Incoming solar radiation (shortwave radiation) = 174 PW (petawatts)

Reflected: Atmosphere = 10 PW Clouds = 35 PW Earth’s surface = 7 PW

Absorbed: Atmosphere = 33 PW Land and ocean = 89 PW

Transfer to heat energy ( longwave radiation) radiated From atmosphere to space 111 PW From surface to space 10 PW 26 PW absorbed by atmosphere

Record these #’sand try to determine

if the energy budget is balanced.

Watch the video

The Greenhouse EffectThe role of greenhouse gases in the

atmosphere is very important to balancing

Earth’s temperature.

Greenhouse gases warm the atmosphere by absorbing and re-emitting heat. Some of the heat that radiates out from the ground is absorbed and re-emitted by greenhouse gases in the troposphere.

Like a blanket on a sleeping person, greenhouse gases act as insulation for the planet. The warming of the atmosphere because of insulation by greenhouse gases is called the greenhouse effect.

Greenhouse gases are the component of the atmosphere that moderate Earth’s temperatures.

Greenhouse Gases:

CO2 – carbon dioxide

H2O – water vapor

CH4 – methane

O3 – ozone

NO & NO2 – nitrous oxides

CFC’s – Chlorofluorocarbons

The way a greenhouse works, light goes in (shortwave radiation), transfers to heat energy (longwave radiation). Longwave radiation can’t penetrate the glass and so it stays inside.

Luckily, our atmosphere holds onto the heat so our planet does not freeze overnight.

However, if we get too much of these gases in

our atmosphere, we will get a ‘runaway’

greenhouse effect like our sister planet, Venus.

Natural ways we acquire greenhouse gases:

Carbon dioxide – respiration, volcanic eruptions, decomposition of plant material

Methane – decoposition of plant material under some conditions, biochemical reactions in stomachs (farts)

Nitrous oxide – produced by bacteria

Ozone – atmospheric processes

CFC’s – NOT natural

There are many human-caused ways of acquiring theses gases.

Look at this diagram and describe the influence man has on the greenhouse effect.