2. Backward Forward Home Exit II. Is the greenhouse effect human enhanced? 1. What is the greenhouse effect? Greenhouse is: a house made of glass allows sunlight (solar energy) to enter it but does not allow all the heat energy inside to escape Sunlight enters the greenhouse through the windows The ground is heated Heat energy cannot pass through the windows Heat energy reflects to the ground and keeps the greenhouse warm inside The ground emits heat to warm the air

3. Backward Forward Home Exit It creates a higher average temperature inside than outside the structure

4. Backward Forward Home Exit The earth’s atmosphere functions like a greenhouse absorb terrestrial radiationBecause water vapour and atmospheric gases absorb terrestrial radiation greenhouse effectThis is known as the greenhouse effect Sun Solar energy passes through the atmosphere Greenhouse gases in the atmosphere trap some of the heat Some of the sun’s energy is reflected back into space

5. Backward Forward Home Exit natural process The greenhouse effect is thus a natural process

6. Backward Forward Home Exit 2. What are greenhouse gases? The two greenhouse gases with the largest concentration in the atmosphere are water vapour and carbon dioxideThe two greenhouse gases with the largest concentration in the atmosphere are water vapour and carbon dioxide Over 95% of the greenhouse effect is the result of atmospheric water vapour in the earth’s atmosphereOver 95% of the greenhouse effect is the result of atmospheric water vapour in the earth’s atmosphere The two greenhouse gases with the largest concentration in the atmosphere are water vapour and carbon dioxideThe two greenhouse gases with the largest concentration in the atmosphere are water vapour and carbon dioxide Over 95% of the greenhouse effect is the result of atmospheric water vapour in the earth’s atmosphereOver 95% of the greenhouse effect is the result of atmospheric water vapour in the earth’s atmosphere

7. Backward Forward Home Exit Water droplets in clouds reflect sunlightWater droplets in clouds reflect sunlight Greenhouse warming moderates the nighttime low temperatures, but will not increase the daytime high temperaturesGreenhouse warming moderates the nighttime low temperatures, but will not increase the daytime high temperatures Water droplets in clouds reflect sunlightWater droplets in clouds reflect sunlight Greenhouse warming moderates the nighttime low temperatures, but will not increase the daytime high temperaturesGreenhouse warming moderates the nighttime low temperatures, but will not increase the daytime high temperatures

8. Backward Forward Home Exit The amount of carbon dioxide in the atmosphere is controlled by the natural carbon cycle

9. Backward Forward Home Exit photosynthesis Green plants take up carbon dioxide during the day in photosynthesis and release it at night

10. Backward Forward Home Exit Animals also release carbon dioxide in respiration

11. Backward Forward Home Exit atmosphere ocean Exchange of carbon dioxide also takes place between the atmosphere and the ocean by: Photosynthesis and respiration of algae and sea animals Absorption of carbon dioxide by seawater

12. Backward Forward Home Exit There is a balance of carbon dioxide in the natural environment

13. Backward Forward Home Exit Oil, coal and natural gas are fossil fuels Gas pipe Coal Oil drilling

14. Backward Forward Home Exit Human activities such as power generation, manufacturing and transportation release large amounts of carbon dioxide through the combustion of fossil fuels

15. Backward Forward Home Exit It takes time for the natural environment to absorb this added and ongoing input of carbon dioxideIt takes time for the natural environment to absorb this added and ongoing input of carbon dioxide There has been an increase of carbon dioxide in the atmosphereThere has been an increase of carbon dioxide in the atmosphere It takes time for the natural environment to absorb this added and ongoing input of carbon dioxideIt takes time for the natural environment to absorb this added and ongoing input of carbon dioxide There has been an increase of carbon dioxide in the atmosphereThere has been an increase of carbon dioxide in the atmosphere

16. Backward Forward Home Exit Production and transportation of coal, natural gas and oilProduction and transportation of coal, natural gas and oil Decomposition of organic wastesDecomposition of organic wastes Rearing of livestockRearing of livestock Sources of methane :

17. Backward Forward Home Exit Agricultural and industrial activities Combustion of solid waste and fossil fuels Sources of nitrous oxide :

18. Backward Forward Home Exit There are other powerful greenhouse gases which come from a variety of industrial processes chlorofluorocarbons hydrofluorocarbons perfluorocarbons sulphur hexafluoride

19. Backward Forward Home Exit Characteristics: concentrations are comparatively low long-lived powerful warmers

20. Backward Forward Home Exit 3. What is the evidence for global warming? Global warming is the increase of the earth’s natural greenhouse effect which raises the average global temperature of the atmosphere near the earth’s surface

21. Backward Forward Home Exit Green gases produced by human activities Click the Screen to Start

22. Backward Forward Home Exit Melting of ice caps and floating ice at the earth’s polesMelting of ice caps and floating ice at the earth’s poles An average global sea-level rise of 10-25 cm over the past 100 yearsAn average global sea-level rise of 10-25 cm over the past 100 years Other evidence of global warming includes:

23. Backward Forward Home Exit Northward migration of some warm-climate fish and tree speciesNorthward migration of some warm-climate fish and tree species Retreat of glaciers on the top of high mountainsRetreat of glaciers on the top of high mountains

24. Backward Forward Home Exit Scientists predict an increase in the average global surface temperature of 0.6-2.5 ℃ over the next fifty years and up to 1.4 to 5.8 ℃ in the next century

25. Backward Forward Home Exit Melting of ice caps Click the Screen to Start