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 o F during a day (like on the moon)
Global Warming Carbon dioxide Even small increases in the amounts of CO 2 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 CO 2 (carbon dioxide) CH 4 (methane) NO 2 (Nitrous Oxide) CFC’s (Chloroflourocarbons) H 2 O (Water Vapor)
Runaway Greenhouse Effect: Venus Atmosphere is mostly carbon dioxide Temperatures can reach A. 300 o F B. 1000 o F C. 500 o F D. 860 o F Artist’s idea of what Venus’ surface might look like
Where Does CO 2 Come From? Combustion of Fossil Fuels in –Power Plants –Cars –Factories
Where Does CH 4 (methane) Come From? –Naturally occurring by- product of rice and cattle farming.
Where Does NO 2 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 H 2 O (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.Methane B.Water Vapor C.CFCs D.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 caps B.floods C.Droughts/ water shortages D.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 CO 2 Conserve energy Recycle & reuse materials And the list goes on!