Chapter 2 - D1. Greenhouse Gases: CFCs

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Chapter 2 - D1. Greenhouse Gases: CFCs

Introduction and Overview A1. Climate System Forcings: Solar Energy A2. Climate System Forcings: Orbital Parameters A3. Climate System Forcings: Planetary Albedo B1. Greenhouse Effect: Atmosphere Structure B2. Greenhouse Effect: Atmosphere Energy Absorption B3. Greenhouse Effect: Gas Concentration C1. Greenhouse Gases: Carbon Dioxide C2. Greenhouse Gases: Methane C3. Greenhouse Gases: Nitrous Oxide D1. Greenhouse Gases: CFCs D2. Greenhouse Gases: HFCs, PFCs, and SF6 D3. Greenhouse Gases: Aerosols

Chapter 2 Labs

Lab 3: CO2 used to school

Chapter 2 Self Checks

Self Checks: 2A1, 2A2, 2A3 Self Checks: 2B1, 2B2, 2B3 Self Checks: 2C1, 2C2, 2C3 Self Checks: 2D1, 2D2, 2D3

Course Reference Links

NASA Climate Center

NOAA Climate Site

NOAA El Niño Site

NOAA Paleoclimate Site

NOAA Climate/Weather Site

Intergovernmental Panel on Climate Change (IPCC)

Introduction

Chlorofluorocarbons (CFCs), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and aerosols are very important greenhouse gases. CFCs, HFCs, and PFCs are all human made and are not produced by any other process but our activities. Chlorofluorocarbons (CFCs) are nontoxic, nonflammable chemicals containing atoms of carbon, chlorine, and fluorine. They are used in the manufacture of aerosol sprays, blowing agents for foams and packing materials, as solvents, and as refrigerants. CFCs owe their existence to accidents that occurred in the early 1900s. Refrigerators in the late 1800s and early 1900s used the toxic gases, ammonia (NH3), methyl chloride, and sulfur dioxide, as refrigerants. After a series of fatal accidents in the 1920s when methyl chloride leaked out of refrigerators, a search for a less toxic replacement begun as a collaborative effort of three American corporations - Frigidaire, General Motors, and Du Pont. CFCs were first synthesized in 1928 by Thomas Midgley, Jr. of General Motors, as safer chemicals for refrigerators used in large commercial applications.

Chlorofluorocarbons - CFCs

Halocarbons are the carbon-based compounds that contain chlorine, fluorine, bromine, or iodine. The compounds that only contain carbon, chlorine, and fluorine are called chlorofluorocarbons (CFCs). Chlorofluorocarbons are exclusively of industrial origin and have only been around for the past 60 years! Chlorofluorocarbons are exceptionally strong greenhouse gases and are also responsible for the destruction of stratospheric ozone. The most publicized of these compounds are those used as coolants in refrigeration and air conditioners, as propellants in spray cans and similar products, and as solvents for industrial purposes. Chlorofluorocarbons are far less abundant than carbon dioxide in the atmosphere, but they are 10,000 times more powerful as a greenhouse gas and can remain in the atmosphere for more than 45 to 100 years. Figure 12 shows the atmospheric concentrations of chlorofluorocarbons. Chlorofluorocarbons are regulated under the 1987 Montreal Protocol and are therefore not addressed in the 1997 Kyoto Protocol.

Figure 12. Two different CFC (CFC-11 and CFC-12) concentrations and growth rates from Northern Hemisphere (NH) and Southern Hemisphere (SH). Note the higher concentrations in the NH, the source of major emissions of CFCs to the atmosphere form human activities before the Montreal Protocol, relative to the SH and the decrease in the growth rate of the two gases in the atmosphere since the late 1980s. CFC concentration given in parts per trillion by volume (pptv).

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