The Greenhouse Effect

• A lot of the light that comes from the sun, doesn’t make it to the surface of the earth.

• X-rays, a lot of incoming IR and UV are absorbed before they reach the surface.

Some of the light that reaches the earth’s surface is changed to IR and is trapped by “Greenhouse Gases” in the atmosphere.

How does a Greenhouse work?• What’s different about the

two waves shown in the picture?– Different wavelengths

• Visible light (from the sun) – Has shorter wavelengths– Can pass through glass/

greenhouse gases.

• Infrared light (heat) – Has longer wavelengths.– Cannot pass through glass/

greenhouse gases and is reflected back.

• Draw this picture.• Label the wavelengths.

The Greenhouse Effect on Earth

• The greenhouse gases act just like the glass in a greenhouse.

The Greenhouse Effect is Good for Life on Earth

• Without the Greenhouse Effect– Reflected IR radiation (heat) would be lost

to space– Earth’s temperature could vary from about

-380 to 250 oF during a day (like on the moon)

Global Warming• Carbon dioxide

Even small increases in the amounts of CO2 in the atmosphere can increase our temperature AND change our climate!

Global Warming

• Most scientists would refer to this as “climate change” rather than global warming, as warming trends are a natural part of the earth’s cycling.

Greenhouse Gases

– Don’t make up a very large percentage of the atmosphere

Greenhouse Gases

• CO2(carbon dioxide)

• CH4 (methane)

• NO2 (Nitrous Oxide)

• CFC’s (Chloroflourocarbons)

• H2O (Water Vapor)

• Describe the trend you see.

Runaway Greenhouse Effect: Venus

• Atmosphere is mostly carbon dioxide

• Temperatures can reach A. 300oF

B. 1000oF

C. 500oF

D. 860oFArtist’s idea of what Venus’ surface might look like

Where Does CO2 Come From?

• Combustion of Fossil Fuels in– Power Plants– Cars– Factories

Where Does CH4 (methane) Come From?

– Naturally occurring by-product of rice and cattle farming.

Where Does NO2 Come From?

• combustion of fossil fuels

• breakdown of fertilizers in soil.

Where Do CFC’s Come From?• Also degrade ozone layer in

addition to being a greenhouse gas

• Come from– Spray cans (banned from spray

cans in 1995)– Coolants in refrigeration systems

and air conditioners – Solvents to clean electronic

components– Blowing agents in the production

of plastic foams. (styrofoam)

Where Does H2O (Water Vapor) Come From?

• It’s all around us.• most abundant

greenhouse gas• not directly

influenced by human activity (So we don’t worry too much about it!)

Which Gases are the Problem?

• Which greenhouse gas is most responsible for global warming?

A. MethaneB. Water VaporC. CFCsD. Carbon Dioxide

Effects of Global Warming• Which of the following are probable results of global

warming due to excessive greenhouse gases?A. thinning of polar ice capsB. floods C. Droughts/ water shortagesD. All of the above In addition to:

• rising sea levels (threatening millions of people) • changing precipitation patterns• heat waves• disruptions of forests and agriculture

• Yet we continue this uncontrolled, global experiment!

What Can We Do About It?

• If we want to reduce the climate change caused by the Greenhouse Effect, we need to reduce Greenhouse Gases:

• Use alternative fuels that don’t emit CO2

• Conserve energy

• Recycle & reuse materials

• And the list goes on!

What Can We Do About It?