The Natural Greenhouse Effect and Anthropogenic (Enhanced) Greenhouse Effect

Definition: “Anthropogenic” = Caused by humans; resulting from human influence on the natural world

The Natural Greenhouse Effect: Notes Natural process! GHGs (greenhouse gases) and clouds absorb infrared radiation from earth’s surface, and radiates it back towards the surface; Heats the atmosphere and surface (keeps earth warm enough for life);

What are some ways that humans contribute GHGs into the atmosphere? Vehicles, industrialization, deforestation (cut down trees which remove CO2 from air) Why is this also called the Enhanced Greenhouse Effect? Natural Greenhouse Effect is strengthened and amplified by human contributions.

Keeling Curve (CO2 Seasonal Variations)

What accounts for the seasonal rise and fall in CO2 in the Keeling Curve? Plant photosynthesis in summer (CO2 goes down), less photosynthesis in winter (CO2 goes up) What planet is cold due to a lack of CO2 in its atmosphere? What planet demonstrates the results of an abundance of atmospheric CO2? Mars (cold), Venus (hot)

Why is CO2 of concern compared to water vapour (another GHG)? Permanence, longer lasting in atmosphere (average: 100 years) What source of evidence do we have for CO2 levels prior to the Industrial Revolution? CO2 dissolved in ice cores, layers in ice cores indicate years/age.

Anthropogenic Sources of Greenhouse Gases (pp. 384-386) Atmospheric Lifetime (years) Carbon dioxide (CO2) Burning fossil fuels (transport, heating, electricity, industry), deforestation, decomposition Most abundant GHG (most important to control) 100-1000 years Methane (CH4) Agriculture (rice farming, cattle ranching), decay in landfills, sewage, mining Potent GHG – absorbs more heat than CO2 12 Nitrous oxide (N2O) Livestock feed and waste, fertilizers 114 Chlorofluoro-carbons (CFCs) Refrigeration (refrigerators, air conditioners, industrial processes 45 (CFC-11), 100 (CFC-12