The Enhanced Greenhouse Effect

The Enhanced Greenhouse Effect: The natural greenhouse effect has been enhanced by human activities, which contribute to the emissions of greenhouse gases

Greenhouse Effect With the greenhouse effect the earths surface temperature, 15°C, is approximately 30°C warmer The process by which infrared and near infrared (visible) radiation warms the earth atmosphere Near infrared (visible) warms the surface Infrared warms the atmosphere Oxygen (O2), nitrogen (N2), and argon (Ar), which make the majority of the atmosphere, do not react significantly with the radiation. Methane, ozone, carbon dioxide, water vapour most significant greenhouse gases more gases = heated atmosphere = more evaporation and clouds = more absorption of radiation = heated atmosphere The earth reflects 30% of the radiation while 70% are absorbed Other greenhouse gases: nitrous oxide, sulphur hexafluoride, hydro fluorocarbons, per fluorocarbons, chlorofluorocarbons

Methane is one of the most potent greenhouse gases Causes 4-9% of greenhouse effect tundra of Siberia is beginning to melt. ice is a form of methane clathrate, ice with large amounts of methane in the crystal structure if melted methane gas will be released into the atmosphere. Methane clathrate deposits are also with in ocean beds depths of +300m where the water temperature will be approximately 2°C. If the ocean temperature rises, methane clathrate deposits will release methane gas in to the ocean drastically influencing environment change. Predicted that 5°C rise would be enough to create extreme changes in marine life. 1ton of methane = 25tons of carbon dioxide in atmosphere

Carbon Dioxide (CO2) Naturally present in the atmosphere in large amounts Earths atmosphere: 5.14 x 1018 kg CO2 in atmosphere: 3.0 x 1015 kg Expected to rise at an unknown rate due to continuing burning of fossil fuels Causes 9-26% of greenhouse effect Oceans absorb approximately one third of all CO2 emissions; they act as a huge carbon sink. But as the water temperature rises, CO2 will be released into the atmosphere to react with radiation from the sun. Warms rapidly in sunlight

Ozone Causes 3-7% of greenhouse effect Created when UV rays react with oxygen in the stratosphere Essential as it filters harmful UV rays Haloalkanes, such as methane, reduce the amount of ozone in the stratosphere Allows for UV rays to reach the troposphere (where most of the oxygen is) causing the creation of ozone A major constituent of smog

Water Vapour Causes 36-70% of greenhouse effect Increase in atmospheric temperature will increase the evaporation of water Results in increasing infrared abortion and increased heat The result of having more water vapour in the atmosphere (troposphere mainly) would theoretically mean that there would be more clouds and thus more radiation reflected back to earth Theoretical because it is unsure if there actually would be more clouds or if the amount of clouds would be reduced

Natural Greenhouse Emissions Volcanoes Oceans Coal combustions Petroleum combustions Natural gas combustions

Human Impact on the Greenhouse Effect From the end of the last Ice Age until the end of the 18th century, the levels of greenhouse gases in the atmosphere remained fairly constant Since the Industrial Revolution, humans have released extra quantities of greenhouse gases into the atmosphere, enhancing the natural greenhouse effect The enhanced greenhouse effect is the direct result of human activities Upsetting the precisely balanced natural systems

Human Activities Removing and burning vegetation Burning fossil fuels Forest build up store of carbon in trees, soil, and fallen leaves When land is cleared, much is rapidly converted back to carbon dioxide Burning fossil fuels Coal, oil, and natural gas contribute to carbon emissions Energy for industrial processes, transportation, agriculture, heating, lighting, etc …

Waste breakdown Agriculture Decaying organic material dumped in landfills create carbon dioxide and methane Agriculture Animals produce methane through digestion Fertilizers release nitrous oxide Rice production in paddy fields generates methane

Gases Contributing to the Greenhouse Effect Chlorofluorocarbon (CFC) are produced by aerosols, refrigerators and air conditioners. They are harmful to the Biosphere because they are destroying the Ozone Layer. Hydrochlorofluorocarbon: a fluorocarbon that is replacing chlorofluorocarbon as a refrigerant and propellant in aerosol cans. Less impact on ozone.

Consequences for Global Warming Increasing concentrations of greenhouse gases will prevent more heat from escaping, increasing the world’s average temperatures Causing global warming and changes in climate Effecting cloud cover, precipitation, wind patterns, duration of seasons, changes in ocean currents, etc …

Changes in weather patterns will lead to: Droughts Heavy precipitation (floods) Declining snow cover and glaciers (contributing to rises in sea levels) Increase in frequency and intensity of tropical cyclones