Greenhouse Gases How does human activity effect them?

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

 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

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

Concentrations and Lifetimes of Atmospheric Greenhouse Gases Greenhouse Gas 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 ppm (700 ppb) (1745ppb) 12 years Nitrous oxide ppm (270 ppm) ( 319 ppb) 120 years CFC-11 Trace amounts ppm (251 ppt) 50 years CFC-12 Trace amounts ppm (538 ppt) 102 years

Anthropogenic Sources of Greenhouse Gases  The phrase “greenhouse gases” is referring to the carbon dioxide (CO 2 ), methane (CH 4 ) and Nitrous Oxide (N 2 O) found in the atmosphere  Chlorofluorocarbons (CFC’s) are also an anthropogenic greenhouse gas

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 CO 2  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

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

Methane (CH 4 )  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

Nitrous Oxide (N 2 O)  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

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

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?

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

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?

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?

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.

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?