Presentation on theme: "The Anthropogenic Greenhouse Effect. Anthropogenic Greenhouse Effect “The enhancement of the natural greenhouse effect due to human activity.” The Problem:"— Presentation transcript:
Anthropogenic Greenhouse Effect “The enhancement of the natural greenhouse effect due to human activity.” The Problem: The increase in greenhouse gas levels may trap more IR in the atmosphere, increasing the average global temperature.
Anthropogenic Greenhouse Gases Humans have little effect on water vapour since it moves rapidly through the water cycle. Humans are increasing the levels of: - Carbon dioxide, CO 2 - Methane, CH 4 - Nitrous oxide, N 2 O - Halocarbons - Ground Level Ozone These do NOT exist naturally. They are additional GH gases added by humans.
Carbon Dioxide Sources: Combustion of fossil fuels. – Transportation, heating, generating electricity, etc. Burning forests to clear land. Cement making.
Methane Sources: Coal and natural gas processing. Agriculture (manure). Landfill sites (garbage).
Nitrous Oxide Sources: Combustion of fossil fuels. Chemical fertilizers. Manure and sewage.
Halocarbons Synthetic compounds containing carbon and halogen elements (F, Cl, Br). Used as cleaners, solvents, and coolants. Includes CFCs (chlorofluorocarbons).
CFCs and the Ozone Layer The ozone layer in the stratosphere absorbs harmful ultraviolet radiation: UV ozone (O 3 ) oxygen (O 2 ) UV rays can cause skin cancer and cataracts. CFC’s act as a catalyst to speed up the breakdown of O 3 : CFC ozone (O 3 ) oxygen (O 2 )
CFCs and the Ozone Layer CFCs banned since 1989. Replaced by other halocarbons... but ALL halocarbons also absorb IR radiation and act as greenhouse gases too!
Global Warming Potential (GWP) A measure of the ability of gases to trap (absorb) IR radiation. carbon dioxide (CO 2 )=1 (least potent) methane (CH 4 )=25 nitrous oxide (N 2 O)=298 hydrofluorocarbon (HFC) =14,800
Why Focus on Carbon? CO 2 has a low GWP but it is the most abundant greenhouse gas. It is also a greenhouse gas that humans directly impact on a large scale. Fossil fuel use has increased exponentially since the 1800s. Fossil fuel extraction and combustion also releases N 2 O and CH 4.
Ground Level Ozone A major component of smog. 13 Produced by photochemical reactions between N 2 O and volatile organic compounds in the presence of sunlight.
Higher levels occur from May to September, between noon and early evening. Very harmful to environment: damages plants and severe respiratory health problems in humans and other animals. 14 Ground Level Ozone