1. Warming Processes: The Greenhouse Effect
The greenhouse effect is a natural phenomenon that keeps Earth warm. Without it, no life would exist on Earth. It would actually be about 33°C (60°F) colder than it is now.

2. Why Greenhouse?
In a greenhouse, light passes through the glass to the interior of the greenhouse. Some of the energy is absorbed by the soil, plants, and glass itself. As the soil and plants warm, they give of heat, which is absorbed by the glass, warming the interior even more. The glass gives off heat, some to the outside, but some to the interior, adding even more heat to the inside. This is how greenhouses can be warm when it’s cold outside.

3. Hot Rods
It is also why the inside of your car gets hot on a cool day when the windows are rolled up. The glass windshield traps heat, so the interior of the car is warmer than the exterior.

4. Gases of the Atmosphere
Most of Earth’s atmosphere consists of nitrogen (78%) and oxygen (21%) gases. Sunlight (and thus heat) passes right through these.
However, other gases such as carbon dioxide, water vapor, and methane absorb heat from the sun.

5. Earth’s Greenhouse Effect

6. REMEMBER!
The greenhouse effect is a natural process that leads to an Earth which is warmer.
It is the reason that our Earth is warm enough to live on.
It is a GOOD thing for life on this planet.

7. Cooling Processes Earth has ways of cooling itself.
Clouds cover 60% of the Earth and reflect 30% of the light.
Earth’s albedo allows the planet to reflect light.
What do you think might happen to Earth’s temperatures if a massive volcano erupted?

8. Effect of Human Activities
Other gases also absorb heat and contribute to the greenhouse effect. Human activity can increase the amount of those gases in the atmosphere.

9. Human Inputs
Increased levels of carbon dioxide are due to burning of fossil fuels, slash and burn agriculture, and automobiles.
Nitrous oxide comes from burning of fossil fuels and fertilizers.
Methane comes from anaerobic breakdown of organic material in swamps, rice paddies, landfills, intestinal tracts (farts), natural gas leaks.
Chlorofluorocarbons (CFCs) come from aerosols, refrigerants, styrofoam. (You’ll hear more about CFCs later.)
Although water vapor accounts for the majority of the greenhouse effect, it has not increased with human activity.

10. Trends in CO2 Concentration
Think…What do you think these peaks and troughs are due to? Remember your cycles of matter?
Greenhouse Effect:
methane (CH4)
nitrous oxide (N2O)

11. Greenhouse Gases Affect on Climate

12. Affect of Activities on Climate

13. Global warming and the greenhouse effect
Global warming is the increase in Earth surface temperature due to an introduction of high levels of greenhouse gases because of human activities.
Global warming is NOT a good thing.

14. A Bit of Good News
The oceans are able to absorb a lot of the CO2 that we produce.
There are limits to what the oceans can absorb, but at least they are reducing the effects.

15. What is the connection between CO2 emissions and global warming?
The Earth experiences a huge range of temperature variations (ice ages).
We really have no idea if the changes we are observing are really due to emission of greenhouse gases by human activity.
However, we DO know how greenhouse gases affect the temperature balance of the Earth.

16. CO2 Emissions and Global Temperatures

17. What are the potential effects of global warming?
Temperature – Scientists think that the average surface temperature should increase 1-3.5°C in the next 100yrs and that the northern hemisphere should heat up more than the southern hemisphere.
Sea level – The sea levels are expected to rise because water expands when it heats up and because land-based ice caps will melt, which would mean that many of the world’s cities would be under water.
Food Production - Agriculture will move northward- may be positive or negative effect.
Weather/Climate – Some places will be wetter, some drier. Might see more weather extremes.
Human health - warmer climate makes better conditions for the growth of disease-causing microorganisms.
Biodiversity - May result in increased productivity by plants and algae.

18. Can anything be done? Reduce CO2 emissions
Charge carbon taxes/polluter pays
switch fuel types
Halt deforestation
Support reforestation
Obtain global ban on CFCs