1. Greenhouse Gases

2. Questions 1.What is the greenhouse effect? 2.What are the 4 main greenhouse gases? 3.Why are small amounts of greenhouse gases good? 4.What are the effects of too much greenhouse gases? 5.How do humans increase greenhouse gases? 6.What are CFCs, and why are they bad? 7.What other planets have greenhouse gases? 8.What causes acid rain? What can it do?

3. Background Earth’s atmosphere is warmed by the Sun’s radiation – Energy from the sun is transferred as heat to the Earth’s atmosphere. – 70% of the radiation from the sun that enters Earth’s atmosphere is absorbed by clouds and Earth’s surface The other 30% escapes back to outer space

4. Greenhouse Effect: Gases in the atmosphere that absorb radiation from the sun and trap it as thermal energy – Solar energy is allowed to enter the atmosphere, but it remains trapped as heat The Greenhouse Effect

6. Types of Gases The main types of greenhouse gases: – Water vapor 35% of all greenhouse gases – Carbon dioxide 51% of all greenhouse gases – Methane 9% of all greenhouse gases – Nitrous Oxide (N 2 O) 5% of all greenhouse gases

7. Positives of Greenhouse Gases Without greenhouse gases, Earth would be so cold there would be no life – Greenhouse gases are naturally occurring! – Normal amounts of greenhouse gases are a positive thing for Earth

8. Effects of excess Greenhouse Gases Effects of excess greenhouse gases: – Greenhouse gases break down the Ozone Layer, which has resulted in several large holes – Greater amounts of greenhouse gases trap more heat from the sun, which increases temperature – Greenhouse gases increase smog – Greenhouse gases lead to human health problems, including asthma and cancer

9. Getting rid of gases Even if we stopped using all greenhouse gases right now, it would take decades to see a decline – Most gases are well mixed in the atmosphere Carbon dioxide: anywhere from 20-200 years to get absorbed, over 1000 years to break down Methane: 10 years to breakdown Nitrous Oxide: 100+ years to break down Water vapor: hours to days (but constantly generated)

10. Human’s Role in Greenhouse Gases Human activity may be increasing levels of greenhouse gases – Distinct and measurable increase in gases since the Industrial Revolution – As we use more fuel, gas, and oil, there has been an increase in greenhouse gases There has also been an increase in the average global temperature during this same time

11. CFCs Chlorofluorocarbons (CFCs): A group of man-made chemical compounds containing chlorine, fluorine and carbon. – They are not found anywhere in nature. They’re used in aerosols, as blowing agents in foam manufacture and in air conditioning. – CFCs travel to the stratsophere where they are broken down by ultraviolet (UV) radiation from the Sun, breaking down the Ozone Layer

12. CFCs continued Although the amounts of CFCs in the atmosphere are very small, they do contribute significantly to the Greenhouse Effect because they are very good at trapping heat. – Molecule for molecule some CFCs are thousands of times stronger than carbon dioxide as greenhouse gases. Since the dangers caused by CFCs to the ozone layer were first discovered, their use has gradually been phased out – However, CFCs have long lifetimes in the atmosphere before they are broken down by sunlight, and so they will continues to increase the greenhouse effect well into the 21 st century.

13. Other planets Other planets in our solar system also have greenhouse gases – Mars Has evidence of past greenhouse effect – Venus Venus has a runaway greenhouse effect – Titan A moon of Saturn

14. Acid Rain One side effect of greenhouse gases is acid rain – Acid rain is caused by emissions of carbon dioxide, sulfur dioxide and nitrogen oxides These compounds then react with the water molecules in the atmosphere to produce acids that fall back to Earth

15. How Acid is Acid Rain? Keep in mind acid rain most likely WILL NOT burn off your face – It can range from the pH of battery acid (BAD!) to lemon juice to vinegar