1. How does human activity effect them?
Greenhouse Gases
How does human activity effect them?

2. Greenhouse Gases: around for thousands of years
Greenhouse gases have been part of our atmosphere for hundreds of thousands of years
Over the past 200 years, the atmospheric levels of most greenhouse gases have increased

4. Anthropogenic GHG
Based on studies done by scientists, they conclude that the increase in greenhouse gases in the atmosphere is due to human activity
This additional amount of human-produced greenhouse gases is called anthropogenic greenhouse gases
The concentration of major greenhouse gases had been increasing since the start of the industrial age

5. Greenhouse Gas Concentrations
In the following table, you can see that atmospheric concentrations of methane and nitrous oxide are much smaller than those of carbon dioxide
However, methane and nitrous oxide molecules are much more powerful than a carbon dioxide molecule in contributing to the greenhouse effect

6. Concentrations and Lifetimes of Atmospheric Greenhouse Gases
Concentration in the atmosphere
Pre-industrial Level
(ppm: parts per million)
2007 Level
(ppb: parts per billion, ppt: parts per trillion)
Approximate atmospheric lifetime
Carbon Dioxide
280 ppm
384 ppm
years
Methane
0.700 ppm (700 ppb)
(1745ppb)
12 years
Nitrous oxide
0.270 ppm (270 ppm)
0.314 ( 319 ppb)
120 years
CFC-11
Trace amounts
ppm (251 ppt)
50 years
CFC-12
ppm (538 ppt)
102 years

7. Anthropogenic Sources of Greenhouse Gases
The phrase “greenhouse gases” is referring to the carbon dioxide (CO2), methane (CH4) and Nitrous Oxide (N2O) found in the atmosphere
Chlorofluorocarbons (CFC’s) are also an anthropogenic greenhouse gas

8. Carbon Dioxide
The most significant greenhouse gas produced by humans today
It accounts for 70% of the anthropogenic greenhouse effect
Burning fossil fuels, such as coal, gasoline, and natural gas) produces CO2
Forests play an important role in determining how much carbon dioxide will remain in the atmosphere. Trees take carbon dioxide from the air and use it in photosynthesis
A tree is considered a carbon sink because it removes carbon from the atmosphere and stores it

9. Carbon Dioxide
About 10% of carbon dioxide emission are due to deforestation
Deforestation stops the forest from absorbing carbon and releases some of the previously absorbed carbon back into the atmosphere as carbon dioxide
The decomposition of trees releases carbon dioxide and methane into the atmosphere and becomes a source for carbon dioxide

10. Methane (CH4)
Methane emissions are about 20% of the total anthropogenic greenhouse gases
Methane is produced from a variety of sources; agricultural activities, decay of organic material, coal mining and natural gas extraction release methane gas that was trapped underground
As mentioned previously, deforestation and forest fires are also sources of methane

11. Nitrous Oxide (N2O)
Under 10% of anthropogenic greenhouse gases is contributed to Nitrous Oxide
Livestock feed and waste management are responsible for two-thirds of these emissions
Other sources are farmers using nitrogen fertilizers and certain industrial processes

12. Chlorofluorocarbons (CFC”S)
CFC’s are commonly used as refrigeration agents
There are no natural sources for CFC’s, they leak out of refrigerators and air conditioners or are released by industrial processes

13. Anthropegenic Greenhouse Gases and Global Temperature
We have evidence that concentrations of greenhouse gases are increasing
We also have evidence that global temperatures are increasing
How do we know whether these changes are related?
What do you think?

14. Ice Core Analyses
In this activity, you will compare ice core data on carbon dioxide with global temperatures over the past years
Open the document
1. Use your current knowledge to write a hypothesis describing the relationship (if any) between carbon dioxide concentrations and global temperature

16. Ice Core Analyses
2. Examine the graph showing carbon dioxide concentrations. What is the highest level of carbon dioxide in the atmosphere over the past years?
3. What is the lowest level of carbon dioxide in the atmosphere over the past years?

17. 4. Today, the concentration of carbon dioxide in the atmosphere is 385 ppm and rising, Compare this value with your values from questions 2 and 3. Which is higher and by what percent?
5. Look at the temperature part of the graph. Identify and record three times over the past years when the temperature changed rapidly.
6. What happened to the concentration of carbon dioxide at the same three times identified above?

18. 7. What is happening to the carbon dioxide concentrations today
7. What is happening to the carbon dioxide concentrations today? What is happening to global temperature?
8. Summarize your findings about carbon dioxide concentration, global temperature and any correlation between them.

19. Conclusion
You have observed that changes in carbon dioxide concentration closely match changes in global temperatures over the past years
The graph does not prove that increases in carbon dioxide concentrations cause global temperature to rise
The graph also does not show that global temperature rise causes increases in carbon dioxide
The graph DOES show a strong correlation between carbon dioxide and global temperature
What might one cause of this correlation be?