The Greenhouse Effect

The Greenhouse Effect

IB Topic 5.2

The greenhouse effect is natural …

• It’s just intensifying due to human activity and pollution

• Causing the overall temperature to increase– Called Global Warming

What is a greenhouse? • Walls and roof are made

of glass• Sunlight penetrates the

glass and warms the plants inside

• Sunlight is not that warm– Due to short wavelengths– Outer space between the

Sun and Earth is hundreds of degrees below freezing

Greenhouse (cont.)

• It’s only when sunlight hits an object that some of the energy is transferred to heat energy– Heat energy has longer wavelengths

• The glass is not as transparent to heat • Heat is trapped inside• Result: the temperature is greater inside

the greenhouse

This happens on Earth, too

• The atmosphere’s ability to retain heat • Greenhouse gases

– Carbon dioxide (CO2), methane, water vapor– Play the role of the glass – Less transparent to heat than light

• As a result:– Some of the heat radiated from Earth’s

surface is trapped– This keeps the atmosphere warm

How does it work?

• 1. Sunlight enters Earth’s atmosphere because gases are transparent to light

• 2. Most sunlight is reflected off of Earth’s surface and travel back out of the atmosphere (that’s why Earth can be seen from outer space)

• 3. Some of the light energy is transformed into heat energy – warms Earth’s surface – radiate much of the heat back to the atmosphere

How does it work?

• 4. Greenhouse gases retain some of the heat and trap it in the atmosphere

• 5. Result: Earth’s natural greenhouse effect keeps Earth warmer than outer space

SUN

Earth

Atmosphere

Some of the heat energy from the Sun reflects off the atmosphere back into space

Heat Radiation

Some heat enters the atmosphere

Some heat energy is absorbed by the

ground

What happens when heat radiation hits the ground?

Some heat energy is reflected back into the

atmosphere

What happens to heat radiation after it is reflected by the ground?

Some heat escapes back into space

Some heat is absorbed by…

…greenhouse gases

CO2

CO2

CO2

CO2

CO2

CO2

CO2

CO2

CO2

CH4

CH4

CH4

CH4

CH4

The more heat radiation that is absorbed by greenhouse gases…… the warmer the atmosphere becomes.

The higher the concentration of greenhouse gases in the atmosphere…… the more heat is absorbed by the atmosphere.

The greenhouse gases

• Carbon dioxide• Methane• Water vapor• Oxides of nitrogen • Concentrations of these gases are

naturally low– Prevents too much heat retention

The problem is … • Human activity

– Demands for food, fuel, & space = excess production of waste gases

• Burning fossil fuels (e.g. gas in cars)• Organic and commercial fertilizers • Industrial processes • Methane (CH4)

– Cooking and heating– Cattle ranching – Waste disposal in landfills

Sources of Greenhouse Gases

Burning fuels produces…

… carbon dioxideRotting vegetation produces…

…methane

Animals produce…

Carbon

dioxide

Methane

(Respiration)(Mostly burps, but

also……some farts!)

Plants remove carbon dioxide from the atmosphere, in a process called…

… photosynthesis

Chopping down trees…

…increases the amount of carbon dioxide in the atmosphere, by…

… reducing the rate of photosynthesis

In conclusion … • Rise in human population and activity = increased levels

of greenhouse gases• These gases absorb heat

– Intensifying Earth’s natural greenhouse effect• However, climate is a complex phenomenon

– Not fully understood • From what is known, a rise in global temperatures:

– Increase in photosynthetic rates– Changes in climate effecting ecosystems– Extinction of certain species– Melting glaciers– A rise in sea levels … flooding of costal area?

What’s Al Gore Up To?

• http://www.ted.com/talks/al_gore_warns_on_latest_climate_trends.html