Global warming 1_notes

Global warming 1_notes - SAS 9 Crisis in the Environment?...

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SAS 9 – Crisis in the Environment? Topic 2: Global Climate Change Fact: The Earth’s surface temperature and oceans are warming. Fact: Human activities are responsible for large increases in greenhouse gases. Debatable: Human activities are exclusively responsible for global warming. Correlation is not causation; however, the preponderance of data suggests that human activities are contributing to global warming. The Earth’s energy balance involves three major components: 1. Solar energy influx 2. Chemistry of the atmosphere (greenhouse gases and aerosols) 3. Albedo - amount of sunlight reflected by the Earth (reflectivity of short-wave radiation) Short-wave radiation – originates from very hot objects such as our sun. Long-wave radiation (heat or infrared) – originates from cooler objects such as the Earth’s surface. Greenhouse Effect Some atmospheric gases have the ability to absorb and reradiate long-wave radiation. The long-wave radiation that gets capture by the atmosphere and reradiated back to the Earth’s surface results in warmer temperatures. In the case of a greenhouse, the glass walls actually absorb and reradiate energy keeping it warmer inside. Greenhouse Gases Because the lower atmosphere (troposphere-extends to 10-15 km) is so well mixed, changes in its composition reflect changes in biogeochemical processes at the global scale. Carbon dioxide (CO 2 ) has increased from 280 ppm in 1800 to approximately 385 ppm today. Although the current level of CO 2 is not unprecedented in the geologic record, the rate of increase is alarming. Primary anthropogenic sources of CO 2 are fossil fuel burning (~75%) and deforestation/burning (~25%), with minor contributions from industrial activities such as steel and cement production. Ozone concentrations are increasing in the troposphere due to air pollution. Chlorofluorocarbons (CFC11 = 280 ppt, CFC12 = 550 ppt) are chemically inert in the troposphere, thus they mix into the
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Global warming 1_notes - SAS 9 Crisis in the Environment?...

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