9.3 The Greenhouse Effect

The Greenhouse Effect

Image Courtesy of WikiMedia

Greenhouse Effect in Review

1. The sun emits energy in the form of light and heat, which travels through space and reaches the Earth's atmosphere.
2. Some of this energy is absorbed by the Earth's surface and re-emitted as infrared radiation, a type of heat.
3. The Earth's atmosphere contains greenhouse gases.
4. Infrared radiation emitted by the Earth is absorbed by greenhouse gases in the atmosphere, which trap heat and cause the temperature of the surface to rise.

Greenhouse Gases and Thermal Retention

Global Warming Potential

Sources of Greenhouse Gases

Carbon Dioxide

• Carbon dioxide naturally occurs as a byproduct of the metabolic reaction of cellular respiration. 
• Volcanic eruptions release a large amount of CO2 and ash, which upon release can have significant short-term effects on climate. Historic large-scale eruptions have been at fault for reducing the global average temperature by blocking solar radiation. 🌋
• The decay of organic matter is another natural source of CO2. As plants and animals die, they decompose, releasing CO2 into the atmosphere. ☠️

• Carbon dioxide is produced during the combustion of fossil fuels. Burning of fossil fuels, including the use of coal, oil, and natural gas for electricity generation, transportation, and industrial processes, is the largest source of CO2 emissions into the atmosphere. 🛢️
• Deforestation is another human-induced source of CO2 emission issues. Trees absorb CO2 from the atmosphere as they grow and photosynthesize. When trees are cut down, the carbon dioxide intake process is disrupted, leading to an increase in atmospheric CO2. An example of this is mass deforestation in the Amazon Rainforest, which is a terrestrial carbon dioxide sink. 🌳
• Land use changes feed into deforestation and CO2 emissions. Changes in land use, such as the conversion of forests to agricultural land can increase the release of CO2 into the atmosphere. 🌾
• Industrial manufacturing and processes also emit carbon dioxide. From cement production to waste decomposition, industries also contribute to increased carbon dioxide. 

Methane

• Wetlands, such as swamps and marshes, produce methane through the decomposition of organic matter.
• In the guts of animals, methane can be produced, meaning animals can create methane through the digestion of their food.
• Wildfires can also release methane into the atmosphere. 🔥

• Fossil fuel extraction and transportation can contribute to methane emissions. The extraction and transportation of fossil fuels, including coal, oil, and natural gas, can release methane into the atmosphere.
• Landfills are a significant source of methane emissions, as organic waste breaks down in low-oxygen conditions and releases methane gas into the atmosphere.
• Agricultural activities are a significant source of increased atmospheric methane. The raising of livestock, including cows, sheep, and goats, is a major source of methane emissions due to the digestion of their food and the decomposition of manure. Increased cattle farming created a large-scale methane increase. 🐄
• Some industrial processes, such as the production of iron and steel, also emit methane.

Water Vapor

• Water vapor is released into the atmosphere through the process of evaporation, which occurs when the sun's energy heats the surface of oceans, lakes, and other bodies of water. 💧
• Plants release water vapor into the atmosphere through a process called transpiration, which occurs when water is absorbed by the roots and transported to the leaves, where it is released into the air through small pores called stomata. 🌿
• Animals release water vapor into the atmosphere through the process of cellular respiration, which occurs when they breathe out air that contains water vapor.

• Some industrial processes, such as the production of electricity, can release water vapor into the atmosphere as a byproduct of burning fossil fuels. 🏭
• Agricultural activities, such as irrigation and the application of fertilizers, can also release water vapor into the atmosphere.

Nitrous Oxide

• Nitrous oxide is naturally produced in soil through the decomposition of organic matter and denitrification during the nitrogen cycle, especially in low-oxygen environments like wetlands and the oceans.
• Lightning also can break down nitrogen molecules and produce nitrous oxide in the atmosphere. ⚡

• Agricultural activities are the main source of increased nitrous oxide. Nitrous oxide is produced in agriculture through the use of nitrogen-based fertilizers and the application of animal manure to fields. 🌽
• The industrial production of nitric acid and the burning of fossil fuels, especially the burning of coal for electric power generation, can also release a significant amount of nitrous oxide into the atmosphere.
• The decomposition of organic waste in landfills and sewage treatment plants can also release nitrous oxide into the atmosphere.

Chlorofluorocarbons (CFCs)

• CFCs were widely used as refrigerants in refrigerators, air conditioners, and other cooling systems. ❄️
• Solvents to clean electronic equipment and manufacture metal.
• CFCs were used as foam-blowing agents in the production of foam products, such as insulation and packaging materials.

Learning Summary