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 Heat Radiation Atmosphere Earth Some of the heat energy from the Sun reflects off the atmosphere back into space Atmosphere Some heat enters the atmosphere Earth

What happens when heat radiation hits the ground? Some heat energy is reflected back into the atmosphere Some heat energy is absorbed by the ground

What happens to heat radiation after it is reflected by the ground? Some heat escapes back into space …greenhouse gases CO2 CH4 Some heat is absorbed by…

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

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… Rotting vegetation produces… … carbon dioxide …methane Animals produce… Methane Carbon dioxide (Mostly burps, but also… (Respiration) …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